In this manner it has been found that fresh basalt exposed to
continually moving water will lose about 0.20 gramme per square
metre of surface per year. The mineral orthoclase, which enters
largely into the constitution of many granites, was found to lose
under the same conditions 0.025 gramme. A glassy lava (obsidian)
rich in silica and in the chemical constituents of an average
granite, was more resistant still; losing but 0.013 gramme per
square metre per year. Hornblende, a mineral

36

abundant in many rocks, lost 0.075 gramme. The mean of the
results showed that 0.08 gramme was washed in a year from each
square metre. Such results give us some indication of the rate at
which the work of solution goes on in the finely divided
soils.[1]

It might be urged that, as the mechanical break up of rocks, and
the production in this way of large surfaces, must be at the
basis of solvent and chemical denudation, these latter activities
should be predominant in the mountains. The answer to this is
that the soils rarely owe their existence to mechanical actions.
The alluvium of the valleys constitutes only narrow margins to
the rivers; the finer _débris_ from the mountains is rapidly
brought into the ocean. The soils which cover the greater part of
continental areas have had a very different origin.

In any quarry where a section of the soil and of the underlying
rock is visible, we may study the mode of formation of soils. Our
observations are, we will suppose, pursued in a granite quarry.
We first note that the material of the soil nearest the surface
is intermixed with the roots of grasses, trees, or shrubs.
Examining a handful of this soil, we see glistening flakes of
mica which plainly are derived from the original granite. Washing
off the finer particles, we find the largest remaining grains are
composed of the all but indestructible quartz.

[1] Proc. Roy. Irish Acad., VIII., Ser. A, p. 21.

37

This also is from the granite. Some few of the grains are of
chalky-looking felspar; again a granitic mineral. What is the
finer silt we have washed off? It, too, is composed of mineral
particles to a great extent; rock dust stained with iron oxide
and intermixed with organic remains, both animal and vegetable.
But if we make a chemical analysis of the finer silt we find that
the composition is by no means that of the granite beneath. The
chemist is able to say, from a study of his results, that there
has been, in the first place, a large loss of material attending
the conversion of the granite to the soil. He finds a
concentration of certain of the more resistant substances of the
granite arising from the loss of the less resistant. Thus the
percentage amount of alumina is increased. The percentage of iron
is also increased. But silica and most other substances show a
diminished percentage. Notably lime has nearly disappeared. Soda
is much reduced; so is magnesia. Potash is not so completely
abstracted. Finally, owing to hydration, there is much more
combined water in the soil than in the rock. This is a typical
result for rocks of this kind.

Deeper in the soil we often observe a change of texture. It has
become finer, and at the same time the clay is paler in colour.
This subsoil represents the finer particles carried by rain from
above. The change of colour is due to the state of the iron which
is less oxidised low down in the soil. Beneath the subsoil the
soil grows

38

again coarser. Finally, we recognise in it fragments of granite
which ever grow larger as we descend, till the soil has become
replaced by the loose and shattered rock. Beneath this the only
sign of weathering apparent in the rock is the rusty hue imparted
by the oxidised iron which the percolating rain has leached from
iron-bearing minerals.

The soil we have examined has plainly been derived in situ from
the underlying rock. It represents the more insoluble residue
after water and acids have done their work. Each year there must
be a very slow sinking of the surface, but the ablation is
infinitesimal.

The depth of such a soil may be considerable. The total surface
exposed by the countless grains of which it is composed is
enormous. In a cubic foot of average soil the surface area of the
grains may be 50,000 square feet or more. Hence a soil only two
feet deep may expose 100,000 square feet for each square foot of
surface area.

It is true that soils formed in this manner by atmospheric and
organic actions take a very long time to grow. It must be
remembered, however, that the process is throughout attended by
the removal in solution: of chemically altered materials.

Considerations such as the foregoing must convince us that while
the accumulation of the detrital sediments around the continents
is largely the result of activities progressing on the steeper
slopes of the land, that is,

39

among the mountainous regions, the feeding of the salts to the
ocean arises from the slower work of meteorological and organic
agencies attacking the molecular constitution of the rocks;
processes which best proceed where the drainage is sluggish and
the quiescent conditions permit of the development of abundant
organic growth and decay.

Statistics of the solvent denudation of the continents support
this view. Within recent years a very large amount of work has
been expended on the chemical investigation of river waters of
America and of Europe. F. W. Clarke has, at the expense of much
labour, collected and compared these results. They are expressed
as so many tonnes removed in solution per square mile per annum.
For North America the result shows 79 tonnes so removed; for
Europe 100 tonnes. Now there is a notable difference between the
mean elevations of these two continents. North America has a mean
elevation of 700 metres over sea level, whereas the mean
elevation of Europe is but 300 metres. We see in these figures
that the more mountainous land supplies less dissolved matter to
the ocean than the land of lower elevation, as our study has led
us to expect.

We have now considered the source of the detrital sediments, as
well as of the dissolved matter which has given to the ocean, in
the course of geological time, its present gigantic load of
salts. It is true there are further solvent and chemical effects
exerted by the sea water

40

upon the sediments discharged into it; but we are justified in
concluding that, relatively to the similar actions taking place
in the soils, the solvent and chemical work of the ocean is
small. The fact is, the deposited detrital sediments around the
continents occupy an area small when contrasted with the vast
stretches of the land. The area of deposition is much less than
that of denudation; probably hardly as much as one twentieth.
And, again, the conditions of aeration and circulation which
largely promote chemical and solvent denudation in the soils are
relatively limited and ineffective in the detrital oceanic
deposits.

The summation of the amounts of dissolved and detrital materials
which denudation has brought into the ocean during the long
denudative history of the Earth, as we might anticipate, reveals
quantities of almost unrealisable greatness. The facts are among
the most impressive which geological science has brought to
light. Elsewhere in this volume they have been mentioned when
discussing the age of the Earth. In the present connection,
however, they are deserving of separate consideration.

The basis of our reasoning is that the ocean owes its saltness
mainly if not entirely to the denudative activities we have been
considering. We must establish this.

We may, in the first place, say that any other view at once
raises the greatest difficulties. The chemical composition of the
detrital sediments which are spread over

41

the continents and which build up the mountains, differs on the
average very considerably from that of the igneous rocks. We know
the former have been derived from the latter, and we know that
the difference in the composition of the two classes of materials
is due to the removal in solution of certain of the constituents
of the igneous rocks. But the ocean alone can have received this
dissolved matter. We know of no other place in which to look for
it. It is true that some part of this dissolved matter has been
again rejected by the ocean; thus the formation of limestone is
largely due to the abstraction of lime from sea water by organic
and other agencies. This, however, in no way relieves us of the
necessity of tracing to the ocean the substances dissolved from
the igneous rocks. It follows that we have here a very causa for
the saltness of the ocean. The view that the ocean "was salt from
the first" is without one known fact to support it, and leaves us
with the burden of the entire dissolved salts of geological time
to dispose of—Where and how?

The argument we have outlined above becomes convincingly strong
when examined more closely. For this purpose we first compare the
average chemical composition of the sedimentary and the igneous
rocks. The following table gives the percentages of the chief
chemical constituents: [1]

[1] F. W. Clarke: _A Preliminary Study of Chemical Denudation_,
p. 13

42

                          Igneous.        Sedimentary.
Silica (SiO₂) -             59.99           58.51
Alumina (Al₂O₃) -           15.04           13.07
Ferric oxide (F₂O₃) -       2.59            3.40
Ferrous oxide (FeO) -       3.34            2.00
Magnesia (MgO) -            3.89            2.52
Lime (CaO) -                 4.81            5.42
Soda (Na₂O) -                3.41            1.12
Potash (K₂O) -               2.95            2.80
Water (H₂O) -                1.92            4.28
Carbon dioxide (CO₂) -       --             4.93
Minor constituents -        2.06            1.95
                          100.00          100.00

In the derivation of the sediments from the igneous rocks there
is a loss by solution of about 33 per cent; _i.e._ 100 tons of
igneous rock yields rather less than 70 tons of sedimentary rock.
This involves a concentration in the sediments of the more
insoluble constituents. To this rule the lime-content appears to
be an exception. It is not so in reality. Its high value in the
sediments is due to its restoration from the ocean to the land.
The magnesia and potash are, also, largely restored from the
ocean; the former in dolomites and magnesian limestones; the
latter in glauconite sands. The iron of the sediments shows
increased oxidation. The most notable difference in the two
analyses appears, however, in the soda percentages. This falls
from 3.41 in the igneous rock to 1.12 in the average sediment.
Indeed, this

43

deficiency of soda in sedimentary rocks is so characteristic of
secondary rocks that it may with some safety be applied to
discriminate between the two classes of substances in cases where
petrological distinctions of other kinds break down.

To what is this so marked deficiency of soda to be ascribed? It
is a result of the extreme solubility of the salts of sodium in
water. This has not only rendered its deposition by evaporation a
relatively rare and unimportant incident of geological history,
but also has protected it from abstraction from the ocean by
organic agencies. The element sodium has, in fact, accumulated in
the ocean during the whole of geological time.

We can use the facts associated with the accumulation of sodium
salts in the ocean as a means of obtaining additional support to
the view, that the processes of solvent denudation are
responsible for the saltness of the ocean. The new evidence may
be stated as follows: Estimates of the amounts of sedimentary
rock on the continents have repeatedly been made. It is true that
these estimates are no more than approximations. But they
undoubtedly _are_ approximations, and as such may legitimately be
used in our argument; more especially as final agreement tends to
check and to support the several estimates which enter into
them.

The most recent and probable estimates of the sediments on the
land assign an average thickness of one mile of

44

secondary rocks over the land area of the world. To this some
increase must be made to allow for similar materials concealed in
the ocean, principally around the continental margins. If we add
10 per cent. and assign a specific gravity of 2.5 we get as the
mass of the sediments 64 x 10¹⁶ tonnes. But as this is about 67
per cent. of the parent igneous rock—_i.e._ the average igneous
rock from which the sediments are derived—we conclude that the
primary denuded rock amounted to a mass of about 95 x 10¹⁶
tonnes.

Now from the mean chemical composition of the secondary rocks we
calculate that the mass of sediments as above determined contains
0.72 x10¹⁶ tonnes of the sodium oxide, Na₂O. If to this amount we
add the quantity of sodium oxide which must have been given to
the ocean in order to account for the sodium salts contained
therein, we arrive at a total quantity of oxide of sodium which
must be that possessed by the primary rock before denudation
began its work upon it. The mass of the ocean being well
ascertained, we easily calculate that the sodium in the ocean
converted to sodium oxide amounts to 2.1 x 10¹⁶ tonnes. Hence
between the estimated sediments and the waters of the ocean we
can account for 2.82 x 10¹⁶ tonnes of soda. When now we put this
quantity back into the estimated mass of primary rock we find
that it assigns to the primary rock a soda percentage of 3.0. On
the average analysis given above this should be 3.41 per cent.
The agreement,

45

all things considered, more especially the uncertainty in the
estimate of the sediments, is plainly in support of the view that
oceanic salts are derived from the rocks; if, indeed, it does not
render it a certainty.

A leading and fundamental inference in the denudative history of
the Earth thus finds support: indeed, we may say, verification.
In the light of this fact the whole work of denudation stands
revealed. That the ocean began its history as a vast fresh-water
envelope of the Globe is a view which accords with the evidence
for the primitive high temperature of the Earth. Geological
history opened with the condensation of an atmosphere of immense
extent, which, after long fluctuations between the states of
steam and water, finally settled upon the surface, almost free of
matter in solution: an ocean of distilled water. The epoch of
denudation then began. It will, probably, continue till the
waters, undergoing further loss of thermal energy, suffer yet
another change of state, when their circulation will cease and
their attack upon the rocks come to an end.

From what has been reviewed above it is evident that the sodium
in the ocean is an index of the total activity of denudation
integrated over geological time. From this the broad facts of the
results of denudation admit of determination with considerable
accuracy. We can estimate the amount of rock which has been
degraded by solvent and chemical actions, and the amount of
sediments which has been derived from it. We are,

46

thus, able to amend our estimate of the sediments which, as
determined by direct observation, served to support the basis of
our argument.

We now go straight to the ocean for the amount of sodium of
denudative origin. There may, indeed, have been some primitive
sodium dissolved by a more rapid denudation while the Earth's
surface was still falling in temperature. It can be shown,
however, that this amount was relatively small. Neglecting it we
may say with safety that the quantity of sodium carried into the
ocean by the rivers must be between 14,000 and 15,000 million
million tonnes: _i.e._ 14,500 x 10¹² tonnes, say.

Keeping the figures to round numbers we find that this amount of
sodium involves the denudation of about 80 x 10¹⁶ tonnes of
average igneous rock to 53 x 1016 tonnes of average sediment.
From these vast quantities we know that the parent rock denuded
during geological time amounted to some 300 million cubic
kilometres or about seventy million cubic miles. The sediments
derived therefrom possessed a bulk of 220 million cubic
kilometres or fifty million cubic miles. The area of the land
surface of the Globe is 144 million square kilometres. The parent
rock would have covered this to a uniform depth of rather more
than two kilometres, and the derived sediment to more than 1.5
kilometres, or about one mile deep.

The slow accomplishment of results so vast conveys some idea of
the great duration of geological time.

47

The foregoing method of investigating the statistics of solvent
denudation is capable of affording information not only as to the
amount of sediments upon the land, but also as to the quantity
which is spread over the floor of the ocean.

We see this when we follow the fate of the 33 per cent. of
dissolved salts which has been leached from the parent igneous
rock, and the mass of which we calculate from the ascertained
mass of the latter, to be 27 x 10¹⁶ tonnes. This quantity was at
one time or another all in the ocean. But, as we saw above, a
certain part of it has been again abstracted from solution,
chiefly by organic agencies. Now the abstracted solids have not
been altogether retained beneath the ocean. Movements of the land
during geological time have resulted in some portion being
uplifted along with other sediments. These substances constitute,
mainly, the limestones.

We see, then, that the 27 x 10¹⁶ tonnes of substances leached
from the parent igneous rocks have had a threefold destination.
One part is still in solution; a second part has been
precipitated to the bottom of the ocean; a third part exists on
the land in the form of calcareous rocks.

Observation on the land sediments shows that the calcareous rocks
amount to about 5 per cent. of the whole. From this we find that
3 x 10¹⁶ tonnes, approximately, of such rocks have been taken
from the ocean. This accounts for one of the three classes of
material

48

into which the original dissolved matter has been divided.
Another of the three quantities is easily estimated: the amount
of matter still in solution in the ocean. The volume of the ocean
is 1,414 million cubic kilometres and its mass is 145 x 10¹⁶
tonnes. The dissolved salts in it constitute 3.4 per cent. of its
mass; or, rather more than 5 x 10¹⁶ tonnes. The limestones on the
land and the salts in the sea water together make up about 8 x
10¹⁶ tonnes. If we, now, deduct this from the total of 27 x 10¹⁶
tonnes, we find that about 19 x 10¹⁶ tonnes must exist as
precipitated matter on the floor of the ocean.

The area of the ocean is 367 x 10¹² square metres, so that if the
precipitated sediment possesses an average specific gravity of
2.5, it would cover the entire floor to a uniform depth of 218
metres; that is 715 feet. This assumes that there was uniform
deposition of the abstracted matter over the floor of the ocean.
Of course, this assumption is not justifiable. It is certain that
the rate of deposition on the floor of the sea has varied
enormously with various conditions—principally with the depth.
Again, it must be remembered that this estimate takes no account
of solid materials otherwise brought into the oceanic deposits;
_e.g._, by wind-transported dust from the land or volcanic
ejectamenta in the ocean depths. It is not probable, however,
that any considerable addition to the estimated mean depth of
deposit from such sources would be allowable.

49

The greatness of the quantities involved in these determinations
is almost awe inspiring. Take the case of the dissolved salts in
the ocean. They are but a fraction, as we have seen, of the total
results of solvent denudation and represent the integration of
the minute traces contributed by the river water. Yet the common
salt (chloride of sodium) alone, contained in the ocean, would,
if abstracted and spread over the dry land as a layer of rock
salt having a specific gravity of 2.2, cover the whole to a depth
of 107 metres or 354 feet. The total salts in solution in the
ocean similarly spread over the land would increase the depth of
the layer to 460 feet. After considering what this means we have
to remember that this amount of matter now in solution in the
seas is, in point of fact, less than a fifth part of the total
dissolved from the rocks during geological time.

The transport by denudation of detrital and dissolved matter from
the land to the ocean has had a most important influence on the
events of geological history. The existing surface features of
the earth must have been largely conditioned by the dynamical
effects arising therefrom. In dealing with the subject of
mountain genesis we will, elsewhere, see that all the great
mountain ranges have originated in the accumulation of the
detrital sediments near the shore in areas which, in consequence
of the load, gradually became depressed and developed into
synclines of many thousands of feet in depth. The most impressive
surface features of the Globe originated

50

in this manner. We will see too that these events were of a
rhythmic character; the upraising of the mountains involving
intensified mechanical denudation over the elevated area and in
this way an accelerated transport of detritus to the sea; the
formation of fresh deposits; renewed synclinal sinking of the sea
floor, and, finally, the upheaval of a younger mountain range.
This extraordinary sequence of events has been determined by the
events of detrital denudation acting along with certain general
conditions which have all along involved the growth of
compressive stresses in the surface crust of the Earth.

The effects of purely solvent denudation are less easily traced,
but, very probably, they have been of not less importance. I
refer here to the transport from the land to the sea of matter in
solution.

Solvent denudation, as observed above, takes place mainly in the
soils and in this way over the more level continental areas. It
has resulted in the removal from the land and transfer to the
ocean of an amount of matter which represents a uniform layer of
one half a kilometre; that is of more than 1,600 feet of rock.
The continents have, during geological time, been lightened to
this extent. On the other hand all this matter has for the
greater part escaped the geosynclines and become uniformly
diffused throughout the ocean or precipitated over its floor
principally on the continental slopes before the great depths are
reached. Of this material the ocean

51

waters contain in solution an amount sufficient to increase their
specific gravity by 2.7 per cent.

Taking the last point first, it is interesting to note the
effects upon the bulk of the ocean which has resulted from the
matter dissolved in it. From the known density of average sea
water we find that 100 ccs. of it weigh just 102.7 grammes. Of
this 3.5 per cent. by weight are solids in solution. That is to
say, 3.594 grammes. Hence the weight of water present is 99.1
grammes, or a volume of 99.1 ccs. From this we see that the salts
present have increased the volume by 0.9 ccs. or 0.9 per cent.

The average depth of the ocean is 2,000 fathoms or 3,700 metres.
The increase of depth due to salts dissolved in the ocean has
been, therefore, 108 feet or 33.24 metres. This result assumes
that there has been no increased elastic compression due to the
increased pressure, and no change of compressional elastic
properties. We may be sure that the rise on the shore line of the
land has not been less than 100 feet.

We see then that as the result of solvent denudation we have to
do with a heavier and a deeper ocean, expanded in volume by
nearly one per cent. and the floor of which has become raised, on
an average, about 700 feet by precipitated sediment.

One of the first conceptions, which the student of geology has to
dismiss from his mind, is that of the immobility or rigidity of
the Earth's crust. The lane, we live on sways even to the gentle
rise and fail of ocean tides

52

around the coasts. It suffers its own tidal oscillations due to
the moon's attractions. Large tracts of semi-liquid matter
underlie it. There is every evidence that the raised features of
the Globe are sustained by such pressures acting over other and
adjacent areas as serve to keep them in equilibrium against the
force of gravity. This state of equilibrium, which was first
recognised by Pratt, as part of the dynamics of the Earth's
crust, has been named isostasy. The state of the crust is that of
"mobile equilibrium."

The transfer of matter from the exposed land surfaces to the
sub-oceanic slopes of the continents and the increase in the
density of the ocean, must all along have been attended by
isostatic readjustment. We cannot take any other view. On the one
hand the land was being lightened; on the other the sea was
increasing in mass and depth and the flanks of the continents
were being loaded with the matter removed from the land and borne
in solution to the ocean. How important the resulting movements
must have been may be gathered from the fact that the existing
land of the Globe stands at a mean elevation of no more than
2,000 feet above sea level. We have seen that solvent denudation
removed over 1,600 feet of rock. But we have no evidence that on
the whole the elevation of land in the past was ever very
different from what it now is.

We have, then, presented to our view the remarkable fact that
throughout the past, and acting with extreme

53

slowness, the land has steadily been melted down into the sea and
as steadily been upraised from the waters. It is possible that
the increased bulk of the ocean has led to a certain diminution
of the exposed land area. The point is a difficult one. One thing
we may without much risk assume. The sub-aereal current of
dissolved matter from the land to the ocean was accompanied by a
sub-crustal flux from the ocean areas to the land areas; the
heated viscous materials creeping from depths far beneath the
ocean floor to depths beneath the roots of the mountains which
arose around the oceans. Such movements took ages for their
accomplishment. Indeed, they have been, probably, continuous all
along and are still proceeding. A low degree of viscosity will
suffice to permit of movements so slow. Superimposed upon these
movements the rhythmic alternations of depression and elevation
of the geosynclines probably resulted in releasing the crust from
local accumulation of strains arising in the more rigid surface
materials. The whole sequence of movements presents an
extraordinary picture of pseudo-vitality—reminding us of the
circulatory and respiratory systems of a vast organism.

All great results in our universe are founded in motions and
forces the most minute. In contemplating the Cause or the Effect
we stand equally impressed with the spectacle presented to us. We
shall now turn from the great effects of denudation upon the
history and evolution of a world and consider for a moment
activities

54

so minute in detail that their operations will probably for ever
elude our bodily senses, but which nevertheless have necessarily
affected and modified the great results we have been
considering.

The ocean a little way from the land is generally so free from
suspended sediments that it has a blackness as of ink. This
blackness is due to its absolute freedom from particles
reflecting the sun's light. The beautiful blue of the Swiss and
Italian lakes is due to the presence of very fine particles
carried into them by the rivers; the finest flour of the
glaciers, which remain almost indefinitely suspended in the
water. But in the ocean it is only in those places where rapid
currents running over shallows stir continually the sediments or
where the fresh water of a great river is carried far from the
land, that the presence of silt is to be observed. The beautiful
phenomenon of the coal-black sea is familiar to every yachtsman
who has sailed to the west of our Islands.[1]

There is, in fact, a very remarkable difference in the manner of
settlement of fine sediments in salt and in fresh water. We are
here brought into contact with one of those subtle yet
influential natural actions the explanation of which involves
scientific advance along many apparently unconnected lines of
investigation.

[1] See Tyndall's Voyage to Algeria in _Fragments of Science._ The
cause of the blue colour of the lakes has been discussed by
various observers, not always with agreement.

55

It is easy to observe in the laboratory the fact of the different
behaviour of salt and fresh water towards finely divided
substances. The nature of the insoluble substance is not
important.

We place, in a good light, two glass vessels of equal dimensions;
the one filled with sea water, the other with fresh water. Into
each we stir the same weight of very finely powdered slate: just
so much as will produce a cloudiness. In a few hours we find the
sea water limpid. The fresh water is still cloudy, however; and,
indeed, may be hardly different in appearance from what it was at
starting. In itself this is a most extraordinary experiment. We
would have anticipated quite the opposite result owing to the
greater density of the sea water.

But a still more interesting experiment remains to be carried
out. In the sea water we have many different salts in solution.
Let us see if these salts are equally responsible for the result
we have obtained. For this purpose we measure out quantities of
sodium chloride and magnesium chloride in the proportion in which
they exist in sea water: that is about as seven to one. We add
such an equal amount of water to each as represents the dilution
of these salts in sea water. Then finally we stir a little of the
finely powdered slate into each. It will be found that the
magnesium chloride, although so much more dilute than the sodium
chloride, is considerably more active in clearing out the
suspension. We may now try such marine salts as magnesium
sulphate,

56

or calcium sulphate against sodium chloride; keeping the marine
proportions. Again we find that the magnesium and calcium salts
are the most effective, although so much more dilute than the
sodium salt.

There is no visible clue to the explanation of these results. But
we must conclude as most probable that some action is at work in
the sea water and in the salt solutions which clumps or
flocculates the sediment. For only by the gathering of the
particles together in little aggregates can we explain their
rapid fall to the bottom. It is not a question of viscosity
(_i.e._ of resistance to the motion of the particles), for the
salt solutions are rather more viscous than the fresh water.
Still more remarkable is the fact that every dissolved substance
will not bring about the result. Thus if we dissolve sugar in
water we find that, if anything, the silt settles more slowly in
the sugar solution than in fresh water.

Now there is one effect produced by the solution of such salts as
we have dealt with which is not produced by such bodies as sugar.
The water is rendered a conductor of electricity. Long ago
Faraday explained this as due to the presence of free atoms of
the dissolved salt in the solution, carrying electric charges. We
now speak of the salt as "ionised." That is it is partly split up
into ions or free electrified atoms of chlorine, sodium,
magnesium, etc., according to the particular salt in solution.
This fact leads us to think that these electrified

57

atoms moving about in the solution may be the cause of the
clumping or flocculation. Such electrified atoms are absent from
the sugar solution: sugar does not become "ionised" when it is
dissolved.

The suspicion that the free electrified atoms play a part in the
phenomenon is strengthened when we recall the remarkable
difference in the action of sodium chloride and magnesium
chloride. In each of the solutions of these substances there are
free chlorine atoms each of which carries a single charge of
negative electricity. As these atoms are alike in both solutions
the different behaviour of the solutions cannot be due to the
chlorine. But the metallic atom is very different in the two
cases. The ionised sodium atom is known to be _monad_ or carries
but _one_ positive charge; whereas the magnesium atom is _diad_ and
carries _two_ positive charges. If, then, we assume that the
metallic, positively electrified atom is in each case
responsible, we have something to go on. It may be now stated
that it has been found by experiment and supported by theory that
the clumping power of an ion rises very rapidly with its valency;
that is with the number of unit charges associated with it. Thus
diads such as magnesium, calcium, barium, etc., are very much
more efficient than monads such as sodium, potassium, etc., and
again, triads such as aluminium are, similarly, very much more
powerful than diad atoms. Here, in short, we have arrived at the
active cause of the phenomenon. Its inner mechanism

58

is, however, harder to fathom. A plausible explanation can be
offered, but a study of it would take us too far. Sufficient has
been said to show the very subtile nature of the forces at work.

We have here an effect due to the sea salts derived by denudation
from the land which has been slowly augmenting during geological
time. It is certain that the ocean was practically fresh water in
remote ages. During those times the silt from the great rivers
would have been carried very far from the land. A Mississippi of
those ages would have sent its finer suspensions far abroad on a
contemporary Gulf stream: not improbably right across the
Atlantic. The earlier sediments of argillaceous type were not
collected in the geosynclines and the genesis of the mountains
was delayed proportionately. But it was, probably, not for very
long that such conditions prevailed. For the accumulation of
calcium salts must have been rapid, and although the great
salinity due to sodium salts was of slow growth the salts of the
diad element calcium must have soon introduced the cooperation of
the ion in the work of building the mountain.

59

THE ABUNDANCE OF LIFE [1]

WE had reached the Pass of Tre Croci[2]and from a point a little
below the summit, looked eastward over the glorious Val Buona.
The pines which clothed the floor and lower slopes of the valley,
extended their multitudes into the furthest distance, among the
many recesses of the mountains, and into the confluent Val di
Misurina. In the sunshine the Alpine butterflies flitted from
stone to stone. The ground at our feet and everywhere throughout
the forests teamed with the countless millions of the small black
ants.

It was a magnificent display of vitality; of the aggressiveness
of vitality, assailing the barren heights of the limestone,
wringing a subsistence from dead things. And the question
suggested itself with new force: why the abundance of life and
its unending activity?

In trying to answer this question, the present sketch
originated.

I propose to refer for an answer to dynamic considerations. It is
apparent that natural selection can only be concerned in a
secondary way. Natural selection defines

[1] Proc. Roy. Dublin Soc., vol. vii., 1890.

[2] In the Dolomites of Southeast Tyrol; during the summer of
1890. Much of what follows was evolved in discussion with my
fellow-traveller, Henry H. Dixon. Much of it is his.

60

a certain course of development for the organism; but very
evidently some property of inherent progressiveness in the
organism must be involved. The mineral is not affected by natural
selection to enter on a course of continual variation and
multiplication. The dynamic relations of the organism with the
environment are evidently very different from those of inanimate
nature.

GENERAL DYNAMIC CONDITIONS ATTENDING INANIMATE ACTIONS

It is necessary, in the first place, to refer briefly to the
phenomena attending the transfer of energy within and into
inanimate material systems. It is not assumed here that these
phenomena are restricted in their sphere of action to inanimate
nature. It is, in fact, very certain that they are not; but while
they confer on dead nature its own dynamic tendencies, it will
appear that their effects are by various means evaded in living
nature. We, therefore, treat of them as characteristic of
inanimate actions. We accept as fundamental to all the
considerations which follow the truth of the principle of the
Conservation of Energy.[1]

[1] "The principle of the Conservation of Energy has acquired so
much scientific weight during the last twenty years that no
physiologist would feel any confidence in an experiment which
showed a considerable difference between the work done by the
animal and the balance of the account of Energy received and
spent."—Clerk Maxwell, _Nature_, vol. xix., p. 142. See also
Helmholtz _On the Conservation of Force._

61

Whatever speculations may be made as to the course of events very
distant from us in space, it appears certain that dissipation of
energy is at present actively progressing throughout our sphere
of observation in inanimate nature. It follows, in fact, from the
second law of thermodynamics, that whenever work is derived from
heat, a certain quantity of heat falls in potential without doing
work or, in short, is dissipated. On the other hand, work may be
entirely converted into heat. The result is the heat-tendency of
the universe. Heat, being an undirected form of energy, seeks, as
it were, its own level, so that the result of this heat-tendency
is continual approach to uniformity of potential.

The heat-tendency of the universe is also revealed in the
far-reaching "law of maximum work," which defines that chemical
change, accomplished without the intervention of external energy,
tends to the production of the body, or system of bodies, which
disengage the greatest quantity of heat.[1] And, again, vast
numbers of actions going on throughout nature are attended by
dissipatory thermal effects, as those arising from the motions of
proximate molecules (friction, viscosity), and from the fall of
electrical potential.

Thus, on all sides, the energy which was once most probably
existent in the form of gravitational potential, is being
dissipated into unavailable forms. We must

[1] Berthelot, _Essai de Mécanique Chimique._

62

recognize dissipation as an inevitable attendant on inanimate
transfer of energy.

But when we come to consider inanimate actions in relation to
time, or time-rate of change, we find a new feature in the
phenomena attending transfer of energy; a feature which is really
involved in general statements as to the laws of physical
interactions.[1] It is seen, that the attitude of inanimate
material systems is very generally, if not in all cases,
retardative of change—opposing it by effects generated by the
primary action, which may be called "secondary" for convenience.
Further, it will be seen that these secondary effects are those
concerned in bringing about the inevitable dissipation.

As example, let us endeavour to transfer gravitational potential
energy contained in a mass raised above the surface of the Earth
into an elastic body, which we can put into compression by
resting the weight upon it. In this way work is done against
elastic force and stored as elastic potential energy. We may deal
with a metal spring, or with a mass of gas contained in a
cylinder fitted with a piston upon which the weight may be
placed. In either case we find the effect of compression is to
raise the temperature of the substance, thus causing its

[1] Helmholtz, _Ice and Glaciers._ Atkinson's collection of his
Popular Lectures. First Series, p.120. Quoted by Tate, _Heat_,
p. 311.

63

expansion or increased resistance to the descent of the weight.
And this resistance continues, with diminishing intensity, till
all the heat generated is dissipated into the surrounding medium.
The secondary effect thus delays the final transfer of energy.

Again, if we suppose the gas in the cylinder replaced by a vapour
in a state of saturation, the effect of increased pressure, as of
a weight placed upon the piston, is to reduce the vapour to a
liquid, thereby bringing about a great diminution of volume and
proportional loss of gravitational potential by the weight. But
this change will by no means be brought about instantaneously.
When a little of the vapour is condensed, this portion parts with
latent heat of vaporisation, increasing the tension of the
remainder, or raising its point of saturation, so that before the
weight descends any further, this heat has to escape from the
cylinder.

Many more such cases might be cited. The heating of india-rubber
when expanded, its cooling when compressed, is a remarkable one;
for at first sight it appears as if this must render it
exceptional to the general law, most substances exhibiting the
opposite thermal effects when stressed. However, here, too, the
action of the stress is opposed by the secondary effects
developed in the substance; for it is found that this substance
contracts when heated, expands when cooled. Again, ice being a
substance which contracts in melting, the effect of pressure is
to facilitate melting, lowering its freezing point. But

64

so soon as a little melting occurs, the resulting liquid calls on
the residual ice for an amount of heat equivalent to the latent
heat of liquefaction, and so by cooling the whole, retards the
change.

Such particular cases illustrate a principle controlling the
interaction of matter and energy which seems universal in
application save when evaded, as we shall see, by the ingenuity
of life. This principle is not only revealed in the researches of
the laboratory; it is manifest in the history of worlds and solar
systems. Thus, consider the effects arising from the aggregation
of matter in space under the influence of the mutual attraction
of the particles. The tendency here is loss of gravitational
potential. The final approach is however retarded by the
temperature, or vis viva of the parts attending collision and
compression. From this cause the great suns of space radiate for
ages before the final loss of potential is attained.

Clerk Maxwell[1] observes on the general principle that less
force is required to produce a change in a body when the change
is unopposed by constraints than when it is subjected to such.
From this if we assume the external forces acting upon a system
not to rise above a certain potential (which is the order of
nature), the constraints of secondary actions may, under certain
circumstances, lead to final rejection of some of the energy, or,
in any

[1] _Theory of Heat_, p. 131.

65

case, to retardation of change in the system—dissipation of
energy being the result.[1]

As such constraints seem inherently present in the properties of
matter, we may summarise as follows:

_The transfer of energy into any inanimate material system is
attended by effects retardative to the transfer and conducive to
dissipation._

Was this the only possible dynamic order ruling in material
systems it is quite certain the myriads of ants and pines never
could have been, except all generated by creative act at vast
primary expenditure of energy. Growth and reproduction would have
been impossible in systems which retarded change at every step
and never proceeded in any direction but in that of dissipation.
Once created, indeed, it is conceivable that, as heat engines,
they might have dragged out an existence of alternate life and
death; life in the hours of sunshine, death in hours of darkness:
no final death, however, their lot, till their parts were simply
worn out by long use, never made good by repair. But the
sustained and increasing activity of organized nature is a fact;
therefore some other order of events must be possible.

[1] The law of Least Action, which has been applied, not alone in
optics, but in many mechanical systems, appears physically based
upon the restraint and retardation opposing the transfer of
energy in material systems.

66

GENERAL DYNAMIC CONDITIONS ATTENDING ANIMATE ACTIONS

What is the actual dynamic attitude of the primary organic
engine—the vegetable organism? We consider, here, in the first
place, not intervening, but resulting phenomena.

The young leaf exposed to solar radiation is small at first, and
the quantity of radiant energy it receives in unit of time cannot
exceed that which falls upon its surface. But what is the effect
of this energy? Not to produce a retardative reaction, but an
accelerative response: for, in the enlarging of the leaf by
growth, the plant opens for itself new channels of supply.

If we refer to "the living protoplasm which, with its unknown
molecular arrangement, is the only absolute test of the cell and
of the organism in general,[1] we find a similar attitude towards
external sources of available energy. In the act of growth
increased rate of assimilation is involved, so that there is an
acceleration of change till a bulk of maximum activity is
attained. The surface, finally, becomes too small for the
absorption of energy adequate to sustain further increase of mass
(Spencer[2]), and the acceleration ceases. The waste going on in
the central parts is then just balanced by the renewal at the
surface. By division, by spreading of the mass, by

[1] Claus, _Zoology_, p. 13.

[2] Geddes and Thomson, _The Evolution of Sex_, p. 220.

67

out-flowing processes, the normal activity of growth may be
restored. Till this moment nothing would be gained by any of
these changes. One or other of them is now conducive to
progressive absorption of energy by the organism, and one or
other occurs, most generally the best of them, subdivision. Two
units now exist; the total mass immediately on division is
unaltered, but paths for the more abundant absorption of energy
are laid open.

The encystment of the protoplasm (occurring under conditions upon
which naturalists do not seem agreed[1]) is to all appearance
protective from an unfavourable environment, but it is often a
period of internal change as well, resulting in a segregation
within the mass of numerous small units, followed by a breakup of
the whole into these units. It is thus an extension of the basis
of supply, and in an impoverished medium, where unit of surface
is less active, is evidently the best means of preserving a
condition of progress.

Thus, in the organism which forms the basis of all modes of life,
a definite law of action is obeyed under various circumstances of
reaction with the available energy of its environment.

Similarly, in the case of the more complex leaf, we see, not only
in the phenomenon of growth, but in its extension in a flattened
form, and in the orientation of greatest surface towards the
source of energy, an attitude towards

[1] However, "In no way comparable with death." Weismann,
_Biological Memoirs_, p. 158.

68

available energy causative of accelerated transfer. There is
seemingly a principle at work, leading to the increase of organic
activity.

Many other examples might be adduced. The gastrula stage in the
development of embryos, where by invagination such an arrangement
of the multiplying cells is secured as to offer the greatest
possible surface consistent with a first division of labour; the
provision of cilia for drawing upon the energy supplies of the
medium; and more generally the specialisation of organs in the
higher developments of life, may alike be regarded as efforts of
the organism directed to the absorption of energy. When any
particular organ becomes unavailing in the obtainment of
supplies, the organ in the course of time becomes aborted or
disappears.[1] On the other hand, when a too ready and liberal
supply renders exertion and specialisation unnecessary, a similar
abortion of functionless organs takes place. This is seen in the
degraded members of certain parasites.

During certain epochs of geological history, the vegetable world
developed enormously; in response probably to liberal supplies of
carbon dioxide. A structural adaptation to the rich atmosphere
occurred, such as was calculated to cooperate in rapidly
consuming the supplies, and to this obedience to a law of
progressive transfer of energy we owe the vast stores of energy
now accumulated

[1] Claus, _Zoology_, p. 157

69

in our coal fields. And when, further, we reflect that this store
of energy had long since been dissipated into space but for the
intervention of the organism, we see definitely another factor in
organic transfer of energy—a factor acting conservatively of
energy, or antagonistically to dissipation.

The tendency of organized nature in the presence of unlimited
supplies is to "run riot." This seems so universal a relation,
that we are safe in seeing here cause and effect, and in drawing
our conclusions as to the attitude of the organism towards
available energy. New species, when they come on the field of
geological history, armed with fresh adaptations, irresistible
till the slow defences of the subjected organisms are completed,
attain enormous sizes under the stimulus of abundant supply, till
finally, the environment, living and dead, reacts upon them with
restraining influence. The exuberance of the organism in presence
of energy is often so abundant as to lead by deprivation to its
self-destruction. Thus the growth of bacteria is often controlled
by their own waste products. A moment's consideration shows that
such progressive activity denotes an accelerative attitude on the
part of the organism towards the transfer of energy into the
organic material system. Finally, we are conscious in ourselves
how, by use, our faculties are developed; and it is apparent that
all such progressive developments must rest on actions which
respond to supplies with fresh demands. Possibly in the present
and ever-

70

increasing consumption of inanimate power by civilised races, we
see revealed the dynamic attitude of the organism working through
thought-processes.

Whether this be so or not, we find generally in organised nature
causes at work which in some way lead to a progressive transfer
of energy into the organic system. And we notice, too, that all
is not spent, but both immediately in the growth of the
individual, and ultimately in the multiplication of the species,
there are actions associated with vitality which retard the
dissipation of energy. We proceed to state the dynamical
principles involved in these manifestations, which appear
characteristic of the organism, as follows:—

_The transfer of energy into any animate material system is
attended by effects conducive to the transfer, and retardative of
dissipation._

This statement is, I think, perfectly general. It has been in
part advanced before, but from the organic more than the physical
point of view. Thus, "hunger is an essential characteristic of
living matter"; and again, "hunger is a dominant characteristic
of living matter,"[1] are, in part, expressions of the statement.
If it be objected against the generality of the statement, that
there are periods in the life of individuals when stagnation and
decay make their appearance, we may answer, that

[1] _Evolution of Sex._ Geddes and Thomson, chap. xvi. See also a
reference to Cope's theory of "Growth Force," in Wallace's
_Darwinism_, p. 425.

71

such phenomena arise in phases of life developed under conditions
of external constraint, as will be urged more fully further on,
and that in fact the special conditions of old age do not and
cannot express the true law and tendency of the dynamic relations
of life in the face of its evident advance upon the Earth. The
law of the unconstrained cell is growth on an ever increasing
scale; and although we assume the organic configuration, whether
somatic or reproductive, to be essentially unstable, so that
continual inflow of energy is required merely to keep it in
existence, this does not vitiate the fact that, when free of all
external constraint, growth gains on waste. Indeed, even in the
case of old age, the statement remains essentially true, for the
phenomena then displayed point to a breakdown of the functioning
power of the cell, an approximation to configurations incapable
of assimilation. It is not as if life showed in these phenomena
that its conditions could obtain in the midst of abundance, and
yet its law be suspended; but as if they represented a
degradation of the very conditions of life, a break up, under the
laws of the inanimate, of the animate contrivance; so that energy
is no longer available to it, or the primary condition, "the
transfer of energy into the animate system," is imperfectly
obeyed. It is to the perfect contrivance of life our statement
refers.

That the final end of all will be general non-availability there
seems little reason to doubt, and the organism, itself dependent
upon differences of potential, cannot

72

hope to carry on aggregation of energy beyond the period when
differences of potential are not. The organism is not accountable
for this. It is being affected by events external to it, by the
actions going on through inanimate agents. And although there be
only a part of the received energy preserved, there is a part
preserved, and this amount is continually on the increase. To see
this it is only necessary to reflect that the sum of animate
energy—capability of doing work in any way through animate
means—at present upon the Earth, is the result, although a small
one, of energy reaching the Earth since a remote period, and
which otherwise had been dissipated in space. In inanimate
actions throughout nature, as we know it, the availability is
continually diminishing. The change is all the one way. As,
however, the supply of available energy in the universe is
(probably) limited in amount, we must look upon the two as simply
effecting the final dissipation of potential in very different
ways. The animate system is aggressive on the energy available to
it, spends with economy, and invests at interest till death
finally deprives it of all. It has heirs, indeed, who inherit
some of its gains, but they, too, must die, and ultimately there
will be no successors, and the greater part must melt away as if
it had never been. The inanimate system responds to the forces
imposed upon it by sluggish changes; of that which is thrust upon
it, it squanders uselessly. The path of the energy is very
different in the two cases.

73

While it is true generally that both systems ultimately result in
the dissipation of energy to uniform potential, the organism can,
as we have seen, under particular circumstances evade the final
doom altogether. It can lay up a store of potential energy which
may be permanent. Thus, so long as there is free oxygen in the
universe, our coalfields might, at any time in the remote future,
generate light and heat in the universal grave.

It is necessary to observe on the fundamental distinction between
the growth of the protoplasm and the growth of the crystal. It is
common to draw comparison between the two, and to point to
metabolism as the chief distinction. But while this is the most
obvious distinction the more fundamental one remains in the
energy relations of the two with the environment.[1] The growth
of the crystal is the result of loss of energy; that of the
organism the result of gain of energy. The crystal represents a
last position of stable equilibrium assumed by molecules upon a
certain loss of kinetic energy, and the formation of the crystal
by evaporation and concentration of a liquid does not, in its
dynamic aspect, differ much from the precipitation of an
amorphous sediment. The organism, on the other hand, represents a
more or less unstable condition formed and maintained by inflow
of energy; its formation, indeed, often attended with a loss of
kinetic energy (fixation of carbon in plants), but, if so,
accompanied by

[1] It appears exceptional for the crystal line configuration to
stand higher in the scale of energy than the amorphous.

74

a more than compensatory increase of potential molecular energy.

Thus, between growth in the living world and growth in the dead
world, the energy relations with the environment reveal a marked
contrast. Again, in the phenomena of combustion, there are
certain superficial resemblances which have led to comparison
between the two. Here again, however, the attitudes towards the
energy of the environment stand very much as + and -. The life
absorbs, stores, and spends with economy. The flame only
recklessly spends. The property of storage by the organism calls
out a further distinction between the course of the two
processes. It secures that the chemical activity of the organism
can be propagated in a medium in which the supply of energy is
discontinuous or localised. The chemical activity of the
combustion can, strictly speaking, only be propagated among
contiguous particles. I need not dwell on the latter fact; an
example of the former is seen in the action of the roots of
plants, which will often traverse a barren place or circumvent an
obstacle in their search for energy. In this manner roots will
find out spots of rich nutriment.

Thus there is a dynamic distinction between the progress of the
organism and the progress of the combustion, or of the chemical
reaction generally. And although there be unstable chemical
systems which absorb energy during reaction, these are
(dynamically) no more than the expansion of the compressed gas.
There is a certain

75

initial capacity in the system for a given quantity of energy;
this satisfied, progress ceases. The progress of the organism in
time is continual, and goes on from less to greater so long as
its development is unconstrained and the supply of energy is
unlimited.

We must regard the organism as a configuration which is so
contrived as to evade the tendency of the universal laws of
nature. Except we are prepared to believe that a violation of the
second law of thermodynamics occurs in the organism, that a
"sorting demon" is at work within it, we must, I think, assume
that the interactions going on among its molecules are
accompanied by retardation and dissipation like the rest of
nature. That such conditions are not incompatible with the
definition of the dynamic attitude of the organism, can be shown
by analogy with our inanimate machines which, by aid of
hypotheses in keeping with the second law of thermodynamics, may
be supposed to fulfil the energy-functions of the plant or
animal, and, in fact, in all apparent respects conform to the
definition of the organism.

We may assume this accomplished by a contrivance of the nature of
a steam-engine, driven by solar energy. It has a boiler, which we
may suppose fed by the action of the engine. It has piston,
cranks, and other movable parts, all subject to resistance from
friction, etc. Now there is no reason why this engine should not
expend its surplus energy in shaping, fitting, and starting into
action other engines:—in fact, in reproductive sacrifice. All

76

these other engines represent a multiplied absorption of energy
as the effects of the energy received by the parent engine, and
may in time be supposed to reproduce themselves. Further, we may
suppose the parent engine to be small and capable of developing
very little power, but the whole series as increasing in power at
each generation. Thus the primary energy relations of the
vegetable organism are represented in these engines, and no
violation of the second law of thermodynamics involved.

We might extend the analogy, and assuming these engines to spend
a portion of their surplus energy in doing work against chemical
forces—as, for example, by decomposing water through the
intervention of a dynamo—suppose them to lay up in this way a
store of potential energy capable of heating the boilers of a
second order of engines, representing the graminivorous animal.
It is obvious without proceeding to a tertiary or carnivorous
order, that the condition of energy in the animal world may be
supposed fulfilled in these successive series of engines, and no
violation of the principles governing the actions going on in our
machines assumed. Organisms evolving on similar principles would
experience loss at every transfer. Thus only a portion of the
radiant energy absorbed by the leaf would be expended in actual
work, chemical and gravitational, etc. It is very certain that
this is, in fact, what takes place.

It is, perhaps, worth passing observation that, from the
nutritive dependence of the animal upon the vegetable,

77

and the fact that a conversion of the energy of the one to the
purposes of the other cannot occur without loss, the mean energy
absorbed daily by the vegetable for the purpose of growth must
greatly exceed that used in animal growth; so that the chemical
potential energy of vegetation upon the earth is much greater
than the energy of all kinds represented in the animal
configurations.[1] It appears, too, that in the power possessed
by the vegetable of remaining comparatively inactive, of
surviving hard times by the expenditure and absorption of but
little, the vegetable constitutes a veritable reservoir for the
uniform supply of the more unstable and active animal.

Finally, on the question of the manner of origin of organic
systems, it is to be observed that, while the life of the present
is very surely the survival of the fittest of the tendencies and
chances of the past, yet, in the initiation of the organised
world, a single chance may have decided a whole course of events:
for, once originated, its own law secures its increase, although
within the new order of actions, the law of the fittest must
assert itself. That such a progressive material system as an
organism was possible, and at some remote period was initiated,
is matter of knowledge; whether or not the initiatory living
configuration was rare and fortuitous, or the probable result of
the general action of physical laws acting among innumerable
chances, must remain matter of

[1] I find a similar conclusion arrived at in Semper's _Animal
Life_, p. 52.

78

speculation. In the event of the former being the truth, it is
evidently possible, in spite of a large finite number of
habitable worlds, that life is non-existent elsewhere. If the
latter is the truth, it is almost certain that there is life in
all, or many of those worlds.

EVOLUTION AND ACCELERATION OF ACTIVITY

The primary factor in evolution is the "struggle for existence."
This involves a "natural selection" among the many variations of
the organism. If we seek the underlying causes of the struggle,
we find that the necessity of food and (in a lesser degree) the
desire for a mate are the principal causes of contention. The
former is much the more important factor, and, accordingly, we
find the greater degree of specialisation based upon it.

The present view assumes a dynamic necessity for its demands
involved in the nature of the organism as such. This assumption
is based on observation of the outcome of its unconstrained
growth, reproduction, and life-acts. We have the same right to
assert this of the organism as we have to assert that retardation
and degradation attend the actions of inanimate machines, which
assertion, also, is based on observation of results. Thus we pass
from the superficial statements that organisms require food in
order to live, or that organisms desire food, to the more
fundamental one that:

_The organism is a configuration of matter which absorbs energy
acceleratively, without limit, when unconstrained._

79

This is the dynamic basis for a "struggle for existence." The
organism being a material system responding to accession of
energy with fresh demands, and energy being limited in amount,
the struggle follows as a necessity. Thus, evolution guiding' the
steps of the energy-seeking organism, must presuppose and find
its origin in that inherent property of the organism which
determines its attitude in presence of available energy.

Turning to the factor, "adaptation," we find that this also must
presuppose, in order to be explicable, some quality of
aggressiveness on the part of the organism. For adaptation in
this or that direction is the result of repulse or victory, and,
therefore, we must presuppose an attack. The attack is made by
the organism in obedience to its law of demand; we see in the
adaptation of the organism but the accumulated wisdom derived
from past defeats and victories.

Where the environment is active, that is living, adaptation
occurs on both sides. Improved means of defence or improved means
of attack, both presuppose activity. Thus the reactions to the
environment, animate and inanimate, are at once the outcome of
the eternal aggressiveness of the organism, and the source of
fresh aggressiveness upon the resources of the medium.

As concerns the "survival of the fittest" (or "natural
selection"), we can, I think, at once conclude that the organism
which best fulfils the organic law under the circumstances of
supply is the "fittest," _ipso facto._ In many

80

cases this is contained in the commonsense consideration, that to
be strong, consistent with concealment from enemies which are
stronger, is best, as giving the organism mastery over foes which
are weaker, and generally renders it better able to secure
supplies. Weismann points out that natural selection favours
early and abundant reproduction. But whether the qualifications
of the "fittest" be strength, fertility, cunning, fleetness,
imitation, or concealment, we are safe in concluding that growth
and reproduction must be the primary qualities which at once
determine selection and are fostered by it. Inherent in the
nature of the organism is accelerated absorption of energy, but
the qualifications of the "fittest" are various, for the supply
of energy is limited, and there are many competitors for it. To
secure that none be wasted is ultimately the object of natural
selection, deciding among the eager competitors what is best for
each.

In short, the facts and generalisations concerning evolution must
presuppose an organism endowed with the quality of progressive
absorption of energy, and retentive of it. The continuity of
organic activity in a world where supplies are intermittent is
evidently only possible upon the latter condition. Thus it
appears that the dynamic attitude of the organism, considered in
these pages, occupies a fundamental position regarding its
evolution.

We turn to the consideration of old age and death, endeavouring
to discover in what relation they stand to the innate
progressiveness of the organism.

81

THE PERIODICITY OF THE ORGANISM AND THE LAW OF PROGRESSIVE
ACTIVITY

The organic system is essentially unstable. Its aggressive
attitude is involved in the phenomenon of growth, and in
reproduction which is a form of growth. But the energy absorbed
is not only spent in growth. It partly goes, also, to make good
the decay which arises from the instability of the organic unit.
The cell is molecularly perishable. It possesses its entity much
as a top keeps erect, by the continual inflow of energy.
Metabolism is always taking place within it. Any other condition
would, probably, involve the difficulties of perpetual motion.

The phenomenon of old age is not evident in the case of the
unicellular organism reproducing by fission. At any stage of its
history all the individuals are of the same age: all contain a
like portion of the original cell, so far as this can be regarded
as persisting where there is continual flux of matter and energy.
In the higher organisms death is universally evident. Why is
this?