Suppose we take a volume of air and squeeze it into 1/100 of its original space. The combativeness of the air-atoms is immensely increased. They pound each other frantically, and become very hot in the process. Now, by cooling the vessel in which they are, we rob them of their energy. They become quiet, but they are much closer than before. Then imagine that all of a sudden we let them loose again. The life is gone out of them, their heat has departed, and on separating they shiver grievously. In other words, the heat contained by the 1/100 volume is suddenly compelled to “spread itself thin” over the whole volume: result—intense cold. And if this air be brought to bear upon a second vessel filled likewise with compressed air, the cold will be even more intense, until at last the air-atoms lose all their strength and collapse into a liquid.

Liquid air is no new thing. Who first made it is uncertain. The credit has been claimed for several people, among them Olzewski, a Pole, and Pictet, a Swiss. As a mere laboratory experiment the manufacture of liquid air in small quantities has been known for twenty years or more. The earlier process was one of terrific compression alone, actually forcing the air molecules by sheer strength into such close contact that their antagonism to one another was temporarily overcome. So expensive was the process that the first ounce of liquid air is estimated to have cost over £600!

In order to make liquid air an article of commerce the most important condition was a wholesale decrease in cost of production. In 1857 C. W. Siemens took out a patent for making the liquid on what is known as the regenerative principle, whereby the compressed air is chilled by expanding a part of it. Professor Dewar—a scientist well known for his researches in the field of liquid gases—had in 1892 produced liquid air by a modification of the principle at comparatively small cost; and other inventors have since then still further reduced the expense, until at the present day there appears to be a prospect of liquid air becoming cheap enough to prove a dangerous rival to steam and electricity.

A company, known as the Liquid Air, Power and Automobile Company, has established large plants in America and England for the manufacture of the liquid on a commercial scale. The writer paid a visit to their depot in Gillingham Street, London, where he was shown the process by Mr. Hans Knudsen, the inventor of much of the machinery there used. The reader will doubtless like to learn the “plain, unvarnished truth” about the creation of this peculiar liquid, and to hear of the freaks in which it indulges—if indeed those may be called freaks which are but obedience to the unchanging laws of Nature.

On entering the factory the first thing that strikes the eye and ear is the monstrous fifty horse-power gas-engine, pounding away with an energy that shakes the whole building. From its ponderous flywheels great leather belts pass to the compressors, three in number, by which the air, drawn from outside the building through special purifiers, is subjected to an increasing pressure. Three dials on the wall show exactly what is going on inside the compressors. The first stands at 90 lbs. to the square inch, the second at 500, and the third at 2200, or rather less than a ton pressure on the area of a penny! The pistons of the low-pressure compressor is ten inches in diameter, but that of the high pressure only two inches, or 1/25 of the area, so great is the resistance to be overcome in the last stage of compression.

Now, if the cycle-pump heats our hands, it will be easily understood that the temperature of the compressors is very high. They are water-jacketed like the cylinders of a gas-engine, so that a circulating stream of cold water may absorb some of the heat. The compressed air is passed through spiral tubes winding through large tanks of water which fairly boils from the fierceness of the heat of compression.

When the air has been sufficiently cooled it is allowed to pass into a small chamber, expanding as it goes, and from the small into a larger chamber, where the cold of expansion becomes so acute that the air-molecules collapse into liquid, which collects in a special receptacle. Arrangements are made whereby any vapour rising from the liquid passes through a space outside the expansion chambers, so that it helps to cool the incoming air and is not wasted.

The liquid-air tank is inside a great wooden case, carefully protected from the heat of the atmosphere by non-conducting substances. A tap being turned, a rush of vapour shoots out, soon followed by a clear, bluish liquid, which is the air we breathe in a fresh guise.

A quantity of it is collected in a saucepan. It simmers at first, and presently boils like water on a fire. The air-heat is by comparison so great that the liquid cannot resist it, and strives to regain its former condition.

You may dip your finger into the saucepan—if you withdraw it again quickly—without hurt. The cushion of air that your finger takes in with it protects you against harm—for a moment. But if you held it in the liquid for a couple of seconds you would be minus a digit. Pour a little over your coat sleeve. It flows harmlessly to the ground, where it suddenly expands into a cloud of chilly vapour.

Put some in a test tube and cork it up. The cork soon flies out with a report—the pressure of the boiling air drives it. Now watch the boiling process. The nitrogen being more volatile—as it boils at a lower temperature than oxygen—passes off first, leaving the pure, blue oxygen. The temperature of this liquid is over 312 degrees below zero (as far below the temperature of the air we breathe as the temperature of molten lead is above it!). A tumbler of liquid oxygen dipped into water is soon covered with a coating of ice, which can be detached from the tumbler and itself used as a cup to hold the liquid. If a bit of steel wire be now twisted round a lighted match and the whole dipped into the cup, the steel flares fiercely and fuses into small pellets; which means that an operation requiring 3000 degrees Fahrenheit has been accomplished in a liquid 300 degrees below zero!

Liquid air has curious effects upon certain substances. It makes iron so brittle that a ladle immersed for a few moments may be crushed in the hands; but, curiously enough, it has a toughening effect on copper and brass. Meat, eggs, fruit, and all bodies containing water become hard as steel and as breakable as glass. Mercury is by it congealed to the consistency of iron; even alcohol, that can brave the utmost Arctic cold, succumbs to it. The writer was present when some thermometers, manufactured by Messrs. Negretti and Zambra, were tested with liquid air. The spirit in the tubes rapidly descended to 250 degrees below zero, then sank slowly, and at about 260 degrees froze and burst the bulb. The measuring of such extreme temperatures is a very difficult matter in consequence of the inability of spirit to withstand them, and special apparatus, registering cold by the shrinkage of metal, must be used for testing some liquid gases, notably liquid hydrogen, which is so much colder than liquid air that it actually freezes it into a solid ice form!

For handling and transporting liquid gases glass receptacles with a double skin from which all air has been exhausted are employed. The surrounding vacuum is so perfect an insulator that a “Dewar bulb” full of liquid air scarcely cools the hand, though the intervening space is less than an inch. This fact is hard to square with the assertion of scientific men that our atmosphere extends but a hundred or two miles from the earth’s surface, and that the recesses of space are a vacuum. If it were so, how would heat reach us from the sun, ninety-two millions of miles away?

One use at least for liquid air is sufficiently obvious. As a refrigerating agent it is unequalled. Bulk for bulk its effect is of course far greater than that of ice; and it has this advantage over other freezing compounds, that whereas slow freezing has a destructive effect upon the tissues of meat and fruit, the instantaneous action of liquid air has no bad results when the thing frozen is thawed out again. The Liquid Air Company therefore proposes erecting depôts at large ports for supplying ships, to preserve the food, cool the cabins in the tropics, and, we hope, to alleviate some of the horrors of the stokehold.

Liquid air is already used in medical and surgical science. In surgery it is substituted for anæsthetics, deadening any part of the body on which an operation has to be performed. In fever hospitals, too, its cooling influence will be welcomed; and liquid oxygen takes the places of compressed oxygen for reviving the flickering flame of life. It will also prove invaluable for divers and submarine boats.

In combination with oil and charcoal liquid air, under the name of “oxyliquit,” becomes a powerful blasting agent. Cartridges of paper filled with the oil and charcoal are provided with a firing primer. When everything is ready for the blasting the cartridges are dropped into a vessel full of liquid air, saturated, placed in position, and exploded. Mr. Knudsen assured the writer that oxyliquit is twice as powerful as nitro-glycerine, and its cost but one-third of that of the other explosive. It is also safer to handle, for in case of a misfire the cartridge becomes harmless in a few minutes, after the liquid air has evaporated.

But the greatest use will be found for liquid air when it exerts its force less violently. It is the result of power; its condition is abnormal; and its return to its ordinary state is accompanied by a great development of energy. If it be placed in a closed vessel it is capable of exerting a pressure of 12,000 lbs. to the square inch. Its return to atmospheric condition may be regulated by exposing it more or less to the heat of the atmosphere. So long as it remains liquid it represents so much stored force, like the electricity stored in accumulators. The Liquid Air Company have at their Gillingham Street depôt a neat little motor car worked by liquid air. A copper reservoir, carefully protected, is filled with the liquid, which is by mechanical means squirted into coils, in which it rapidly expands, and from them passes to the cylinders. A charge of eighteen gallons will move the car forty miles at an average pace of twelve miles an hour, without any of the noise, dirt, smell, or vapour inseparable from the employment of steam or petroleum. The speed of the car is regulated by the amount of liquid injected into the expansion coils.

We now come to the question of cost—the unromantic balance in which new discoveries are weighed and many found wanting. The storage of liquid air is feasible for long periods. (A large vacuum bulb filled and exposed to the atmosphere had some of the liquid still unevaporated at the end of twenty-two days.) But will it be too costly for ordinary practical purposes now served by steam and electricity? The managers of the Liquid Air Company, while deprecating extravagant prophecies about the future of their commodity, are nevertheless confident that it has “come to stay.” With the small 50 horse-power plant its production costs upwards of one shilling a gallon, but with much larger plant of 1000 horse-power they calculate that the expenses will be covered and a profit left if they retail it at but one penny the gallon. This great reduction in cost arises from the economising of “waste energy.” In the first place the power of expansion previous to the liquefaction of the compressed air will be utilised to work motors. Secondly, the heat of the cooling tanks will be turned to account, and even the “exhaust” of a motor would be cold enough for ordinary refrigerating. It is, of course, impossible to get more out of a thing than has been put into it; and liquid air will therefore not develop even as much power as was required to form it. But its handiness and cleanliness strongly recommend it for many purposes, as we have seen; and as soon as it is turned out in large quantities new uses will be found for it. Perhaps the day will come when liquid-air motors will replace the petrol car, and in every village we shall see hung out the sign, “Liquid air sold here.” As the French say, “Qui vivra verra.”

HORSELESS CARRIAGES.

A body of enterprising Manchester merchants, in the year 1754, put on the road a “flying coach,” which, according to their special advertisement, would, “however incredible it may appear, actually, barring accidents, arrive in London in four and a half days after leaving Manchester.” According to the Lord Chancellor of the time such swift travelling was considered dangerous as well as wonderful—the condition of the roads might well make it so—and also injurious to health. “I was gravely advised,” he says, “to stay a day in York on my journey between Edinburgh and London, as several passengers who had gone through without stopping had died of apoplexy from the rapidity of the motion.”

As the coach took a fortnight to pass from the Scotch to the English capital, at an average pace of between three and four miles an hour, it is probable that the Chancellor’s advisers would be very seriously indisposed by the mere sight of a motor-car whirling along in its attendant cloud of dust, could they be resuscitated for the purpose. And we, on the other hand, should prefer to get out and walk to “flying” at the safe speed of their mail coaches.

The improvement of highroads, and road-making generally, accelerated the rate of posting. In the first quarter of the nineteenth century an average of ten or even twelve miles an hour was maintained on the Bath Road. But that pace was considered inadequate when the era of the “iron horse” commenced, and the decay of stage-driving followed hard upon the growth of railways. What should have been the natural successor of the stage-coach was driven from the road by ill-advised legislation, which gave the railroads a monopoly of swift transport, which has but lately been removed.

The history of the steam-coach, steam-carriage, automobile, motor-car—to give it its successive names—is in a manner unique, showing as it does, instead of steady development of a practical means of locomotion, a sudden and decisive check to an invention worthy of far better treatment than it received. The compiler of even a short survey of the automobile’s career is obliged to divide his account into two main portions, linked together by a few solitary engineering achievements.

The first period (1800-1836), will, without any desire to arrogate for England more than her due or to belittle the efforts of any other nations, be termed the English period, since in it England took the lead, and produced by far the greatest number of steam-carriages. The second (1870 to the present day) may, with equal justice, be styled the Continental period, as witnessing the great developments made in automobilism by French, German, Belgian, and American engineers: England, for reasons that will be presently noticed, being until quite recently too heavily handicapped to take a part in the advance.

Historical.—It is impossible to discover who made the first self-moving carriage. In the sixteenth century one Johann Haustach, a Nuremberg watchmaker, produced a vehicle that derived its motive power from coiled springs, and was in fact a large edition of our modern clockwork toys. About the same time the Dutch, and among them especially one Simon Stevin, fitted carriages with sails, and there are records of a steam-carriage as early as the same century.

But the first practical, and at least semi-successful, automobile driven by internal force was undoubtedly that of a Frenchman, Nicholas Joseph Cugnot, who justly merits the title of father of automobilism. His machine, which is to-day one of the most treasured exhibits in the Paris Museum of Arts and Crafts, consisted of a large carriage, having in front a pivoted platform bearing the machinery, and resting on a solid wheel, which propelled as well as steered the vehicle. The boiler, of stout riveted copper plates, had below it an enclosed furnace, from which the flames passed upwards through the water through a funnel. A couple of cylinders, provided with a simple reversing gear, worked a ratchet that communicated motion to the driving-wheel. This carriage did not travel beyond a very slow walking pace, and Cugnot therefore added certain improvements, after which (1770) it reached the still very moderate speed of four miles an hour, and distinguished itself by charging and knocking down a wall, a feat that is said to have for a time deterred engineers from developing a seemingly dangerous mode of progression.

Ten years later Dallery built a steam car, and ran it in the streets of Amiens—we are not told with what success; and before any further advance had been made with the automobile the French Revolution put a stop to all inventions of a peaceful character among our neighbours.

In England, however, steam had already been recognised as the coming power. Richard Trevethick, afterwards to become famous as a railroad engineer, built a steam motor in 1802, and actually drove it from Cambourne to Plymouth, a distance of ninety miles. But instead of following up this success, he forsook steam-carriages for the construction of locomotives, leaving his idea to be expanded by other men, who were convinced that a vehicle which could be driven over existing roads was preferable to one that was helpless when separated from smooth metal rails. Between the years 1800 and 1836 many steam vehicles for road traffic appeared from time to time, some, such as David Gordon’s (propelled by metal legs pressing upon the ground), strangely unpractical, but the majority showing a steady improvement in mechanical design.

As it will be impossible, without writing a small book, to name all the English constructors of this period, we must rest content with the mention of the leading pioneers of the new locomotion.

Sir Goldsworthy Gurney, an eminent chemist, did for mechanical road propulsion what George Stephenson was doing for railway development. He boldly spent large sums on experimental vehicles, which took the form of six-wheeled coaches. The earliest of these were fitted with legs as well as driving-wheels, since he thought that in difficult country wheels alone would not have sufficient grip. (A similar fallacy was responsible for the cogged wheels on the first railways.) But in the later types legs were abandoned as unnecessary. His coaches easily climbed the steepest hills round London, including Highgate Hill, though a thoughtful mathematician had proved by calculations that a steam-carriage, so far from mounting a gradient, could not, without violating all natural laws, so much as move itself on the level!

Having satisfied himself of their power, Gurney took his coaches further afield. In 1829 was published the first account of a motor trip made by him and three companions through Reading, Devizes, and Melksham. The pace was, we read, at first only about six miles an hour, including stoppages. They drove very carefully to avoid injury to the persons or feelings of the country folk; but at Melksham, where a fair was in progress, they had to face a shower of stones, hurled by a crowd of roughs at the instigation of some coaching postilions, who feared losing their livelihood if the new method of locomotion became general. Two of the tourists were severely hurt, and Gurney was obliged to take shelter in a brewery, where constables guarded his coach. On the return journey the party timed their movements so as to pass through Melksham while the inhabitants were all safely in bed.

The coach ran most satisfactorily, improving every mile. “Our pace was so rapid,” wrote one of the company, “that the horses of the mail-cart which accompanied us were hard put to it to keep up with us. At the foot of Devizes Hill we met a coach and another vehicle, which stopped to see us mount this hill, an extremely steep one. We ascended it at a rapid rate. The coach and passengers, delighted at this unexpected sight, honoured us with shouts of applause.”

In 1830 Messrs. Ogle and Summers completely beat the road record on a vehicle fitted with a tubular boiler. This car, put through its trials before a Special Commission of the House of Commons, attained the astonishing speed of 35 miles an hour on the level, and mounted a hill near Southampton at 24-1/2 miles an hour. It worked at a boiler pressure of 250 lbs. to the square inch, and though not hung on springs, ran 800 miles without a breakdown. This performance appears all the more extraordinary when we remember the roads of that day were not generally as good as they are now, and that in the previous year Stephenson’s “Rocket,” running on rails, had not reached a higher velocity.

The report of the Parliamentary Commission on horseless carriages was most favourable. It urged that the steam-driven car was swifter and lighter than the mail-coaches; better able to climb and descend hills; safer; more economical; and less injurious to the roads; and, in conclusion, that the heavy charges levied at the toll-gates (often twenty times those on horse vehicles) were nothing short of iniquitous.

As a result of this report, motor services, inaugurated by Walter Hancock, Braithwayte, and others, commenced between Paddington and the Bank, London and Greenwich, London and Windsor, London and Stratford. Already, in 1829, Sir Charles Dance had a steam-coach running between Cheltenham and Gloucester. In four months it ran 3500 miles and carried 3000 passengers, traversing the nine miles in three-quarters of an hour; although narrow-minded landowners placed ridges of stone eighteen inches deep on the road by way of protest.

The most ambitious service of all was that between London and Birmingham, established in 1833 by Dr. Church. The rolling-stock consisted of a single very much decorated coach.

The success of the road-steamer seemed now assured, when a cloud appeared on the horizon. It had already been too successful. The railway companies were up in arms. They saw plainly that if once the roads were covered with vehicles able to transport the public at low fares quickly from door to door on existing thoroughfares, the construction of expensive railroads would be seriously hindered, if not altogether stopped. So, taking advantage of two motor accidents, the companies appealed to Parliament—full of horse-loving squires and manufacturers, who scented profit in the railways—and though scientific opinion ran strongly in favour of the steam-coach, a law was passed in 1836 which rendered the steamers harmless by robbing them of their speed. The fiat went forth that in future every road locomotive should be preceded at a distance of a hundred yards by a man on foot carrying a red flag to warn passengers of its approach. This law marks the end of the first period of automobilism as far as England is concerned. At one blow it crippled a great industry, deprived the community of a very valuable means of transport, and crushed the energies of many clever inventors who would soon, if we may judge by the rapid advances already made in construction, have brought the steam-carriage to a high pitch of perfection. In the very year in which they were suppressed the steam services had proved their efficiency and safety. Hancock’s London service alone traversed 4200 miles without serious accident, and was so popular that the coaches were generally crowded. It is therefore hard to believe that these vehicles did not supply a public want, or that they were regarded by those who used them as in any way inferior to horse-drawn coaches. Yet ignorant prejudice drove them off the road for sixty years; and to-day it surprises many Englishmen to learn that what is generally considered a novel method of travelling was already fairly well developed in the time of their grandfathers.

Second Period (1870 onwards).—To follow the further development of the automobile we must cross the Channel once again. French invention had not been idle while Gurney and Hancock were building their coaches. In 1835 M. Dietz established a service between Versailles and Paris, and the same year M. D’Asda carried out some successful trials of his steam “diligence” under the eyes of Royalty. But we find that for the next thirty-five years the steam-carriage was not much improved, owing to want of capital among its French admirers. No Gurney appeared, ready to spend his thousands in experimenting; also, though the law left road locomotion unrestricted, the railways offered a determined opposition to a possibly dangerous rival. So that, on the whole, road transport by steam fared badly till after the terrible Franco-Prussian war, when inventors again took courage. M. Bollée, of Mans, built in 1873 a car, “l’Obéissante,” which ran from Mans to Paris; and became the subject of allusions in popular songs and plays, while its name was held up as an example to the Paris ladies. Three years later he constructed a steam omnibus to carry fifty persons, and in 1878 exhibited a car that journeyed at the rate of eighteen miles an hour from Paris to Vienna, where it aroused great admiration.

After the year 1880 French engineers divided their attention between the heavy motor omnibus and light vehicles for pleasure parties. In 1884 MM. Bouton and Trépardoux, working conjointly with the Comte de Dion, produced a steam-driven tricycle, and in 1887 M. Serpollet followed suit with another, fitted with the peculiar form of steam generator that bears his name. Then came in 1890 a very important innovation, which has made automobilism what it now is. Gottlieb Daimler, a German engineer, introduced the petrol gas-motor. Its comparative lightness and simplicity at once stamped it as the thing for which makers were waiting. Petrol-driven vehicles were soon abroad in considerable numbers and varieties, but they did not attract public attention to any great extent until, in 1894, M. Pierre Giffard, an editor of the Petit Journal, organised a motor race from Paris to Rouen. The proprietors of the paper offered handsome prizes to the successful competitors. There were ten starters, some on steam, others on petrol cars. The race showed that, so far as stability went, Daimler’s engine was the equal of the steam cylinder. The next year another race of a more ambitious character was held, the course being from Paris to Bordeaux and back. Subscriptions for prizes flowed in freely. Serpollet, de Dion, and Bollée prepared steam cars that should win back for steam its lost supremacy, while the petrol faction secretly built motors of a strength to relegate steam once and for all to a back place. Electricity, too, made a bid unsuccessfully for the prize in the Jeantaud car, a special train being engaged in advance to distribute charged accumulators over the route. The steamers broke down soon after the start, so that the petrol cars “walked over” and won a most decisive victory.

The interest roused in the race led the Comte de Dion to found the Automobile Club of France, which drew together all the enthusiastic admirers of the new locomotion. Automobilism now became a sport, a craze. The French, with their fine straight roads, and a not too deeply ingrained love of horseflesh, gladly welcomed the flying car, despite its noisy and malodorous properties.

Orders flowed in so freely that the motor makers could not keep pace with the demand, or promise delivery within eighteen months. Rich men were therefore obliged to pay double prices if they could find any one willing to sell—a state of things that remains unto this day with certain makes of French cars. Poorer folks contented themselves with De Dion motor tricycles, which showed up so well in the 1896 Paris-Marseilles race; or with the neat little three-wheeled cars of M. Bollée. Motor racing became the topic of the hour. Journals were started for the sole purpose of recording the doings of motorists; and few newspapers of any popularity omitted a special column of motor news. Successive contests on the highroads at increasing speeds attracted increased interest. The black-goggled, fur-clad chauffeur who carried off the prizes found himself a hero.

In short, the hold which automobilism has over our neighbours may be gauged from the fact that in 1901 it was estimated that nearly a thousand motor cars assembled to see the sport on the Longchamps Course (the scene of that ultra-“horsey” event, the Grand Prix), and the real interest of the meet did not centre round horses of flesh and blood.

The French have not a monopoly of devotion to automobilism. The speedy motor car is too much in accord with the bustling spirit of the age; its delights too easily appreciated to be confined to one country. Allowing France the first place, America, Germany, and Belgium are not far behind in their addiction to the “sport,” and even in Britain, partially freed since 1896 from the red-flag tyranny, thanks to the efforts of Sir David Salomons, there are most visible signs that the era of the horse is beginning its end.

Types of Car.

Automobiles may be classified according to the purpose they serve, according to their size and weight, or according to their motive power. We will first review them under the latter head.

A. Petrol.—The petrol motor, suitable alike for large cars of 40 to 60 horse-power and for the small bicycle weighing 70 lbs. or so, at present undoubtedly occupies the first place in popular estimation on account of its comparative simplicity, which more than compensates certain defects that affect persons off the vehicle more than those on it—smell and noise.

The chief feature of the internal explosion motor is that at one operation it converts fuel directly into energy, by exploding it inside a cylinder. It is herein more economical than steam, which loses power while passing from the boiler to the driving-gear.

Petrol cycles and small cars have usually only one cylinder, but large vehicles carry two, three, and sometimes four cylinders. Four and more avoid that bugbear of rotary motion, “dead points,” during which the momentum of the machinery alone is doing work; and for that reason the engines of racing cars are often quadrupled.

For the sake of simplicity we will describe the working of a single cylinder, leaving the reader to imagine it acting alone or in concert with others as he pleases.

In the first place the fuel, petrol, is a very inflammable distillation of petroleum: so ready to ignite that it must be most rigorously guarded from naked lights; so quick to evaporate that the receptacles containing it, if not quite airtight, will soon render it “stale” and unprofitable for motor driving.

The engine, to mention its most important parts, consists of a single-action cylinder (giving a thrust one way only); a heavy flywheel revolving in an airtight circular case, and connected to the piston by a hinged rod which converts the reciprocating movement of the piston into a rotary movement of the crank-shaft built in with the wheel; inlet and outlet valves; a carburettor for generating petrol gas, and a device to ignite the gas-and-air mixture in the cylinder.

The action of the engine is as follows: as the piston moves outwards in its first stroke it sucks through the inlet valve a quantity of mixed air and gas, the proportions of which are regulated by special taps. The stroke ended, the piston returns, compressing the mixture and rendering it more combustible. Just as the piston commences its second outward stroke an electric spark passed through the mixture mechanically ignites it, and creates an explosion, which drives the piston violently forwards. The second return forces the burnt gas through the exhaust-valve, which is lifted by cog-gear once in every two revolutions of the crank, into the “silencer.” The cycle of operations is then repeated.

We see that during three-quarters of the “cycle”—the suction, compression, and expulsion—the work is performed entirely by the flywheel. It follows that a single-cylinder motor, to work at all, must rotate the wheel at a high rate. Once stopped, it can be restarted only by the action of the handle or pedals; a task often so unpleasant and laborious that the driver of a car, when he comes to rest for a short time only, disconnects his motor from the driving-gear and lets it throb away idly beneath him.

The means of igniting the gas in the cylinders may be either a Bunsen burner or an electric spark. Tube ignition is generally considered inferior to electrical because it does not permit “timing” of the explosion. Large cars are often fitted with both systems, so as to have one in reserve should the other break down.

Electrical ignition is most commonly produced by the aid of an intensity coil, which consists of an inner core of coarse insulated wire, called the primary coil; and an outer, or secondary coil, of very fine wire. A current passes at intervals, timed by a cam on the exhaust-valve gear working a make-and-break contact blade, from an accumulator through the primary coil, exciting by induction a current of much greater intensity in the secondary. The secondary is connected to a “sparking plug,” which screws into the end of the cylinder, and carries two platinum points about 1/32 of an inch apart. The secondary current leaps this little gap in the circuit, and the spark, being intensely hot, fires the compressed gas. Instead of accumulators a small dynamo, driven by the motor, is sometimes used to produce the primary current.

By moving a small lever, known as the “advancing lever,” the driver can control the time of explosion relatively to the compression of the gas, and raise or lower the speed of the motor.

The strokes of the petrol-driven cylinder are very rapid, varying from 1000 to 3000 a minute. The heat of very frequent explosions would soon make the cylinder too hot to work were not measures adopted to keep it cool. Small cylinders, such as are carried on motor cycles, are sufficiently cooled by a number of radiating ribs cast in a piece with the cylinder itself; but for large machines a water jacket or tank surrounding the cylinder is a necessity. Water is circulated through the jacket by means of a small centrifugal pump working off the driving gear, and through a coil of pipes fixed in the front of the car to catch the draught of progression. So long as the jacket and tubes are full of water the temperature of the cylinder cannot rise above boiling point.

Motion is transmitted from the motor to the driving-wheels by intermediate gear, which in cycles may be only a leather band or couple of cogs, but in cars is more or less complicated. Under the body of the car, running usually across it, is the countershaft, fitted at each end with a small cog which drives a chain passing also over much larger cogs fixed to the driving-wheels. The countershaft engages with the cylinder mechanism by a “friction-clutch,” a couple of circular faces which can be pressed against one another by a lever. To start his car the driver allows the motor to obtain a considerable momentum, and then, using the friction lever, brings more and more stress on to the countershaft until the friction-clutch overcomes the inertia of the car and produces movement.

Gearing suitable for level stretches would not be sufficiently powerful for hills: the motor would slow and probably stop from want of momentum. A car is therefore fitted with changing gears, which give two or three speeds, the lower for ascents, the higher for the level: and on declines the friction-clutch can be released, allowing the car to “coast.”

B. Steam Cars.—Though the petrol car has come to the front of late years it still has a powerful rival in the steam car. Inventors have made strenuous efforts to provide steam-engines light enough to be suitable for small pleasure cars. At present the Locomobile (American) and Serpollet (French) systems are increasing their popularity. The Locomobile, the cost of which (about £120) contrasts favourably with that of even the cheaper petrol cars, has a small multitubular boiler wound on the outside with two or three layers of piano wire, to render it safe at high pressures. As the boiler is placed under the seat it is only fit and proper that it should have a large margin of safety. The fuel, petrol, is passed through a specially designed burner, pierced with hundreds of fine holes arranged in circles round air inlets. The feed-supply to the burner is governed by a spring valve, which cuts off the petrol automatically as soon as the steam in the boiler reaches a certain pressure. The locomobile runs very evenly and smoothly, and with very little noise, a welcome change after the very audible explosion motor.

The Serpollet system is a peculiar method of generating steam. The boiler is merely a long coil of tubing, into which a small jet of water is squirted by a pump at every stroke of the cylinders. The steam is generated and used in a moment, and the speed of the machine is regulated by the amount of water thrown by the pumps. By an ingenious device the fuel supply is controlled in combination with the water supply, so that there may not be any undue waste in the burner.

C. Electricity.—Of electric cars there are many patterns, but at present they are not commercially so practical as the other two types. The great drawbacks to electrically-driven cars are the weight of the accumulators (which often scale nearly as much as all the rest of the vehicle), and the difficulty of getting them recharged when exhausted. We might add to these the rapidity with which the accumulators become worn out, and the consequent expense of renewal. T. A. Edison is reported at work on an accumulator which will surpass all hitherto constructed, having a much longer life, and weighing very much less, power for power. The longest continuous run ever made with electricity, 187 miles at Chicago, compares badly with the feat of a petrol car which on November 23, 1900, travelled a thousand miles on the Crystal Palace track in 48 hours 24 minutes, without a single stop. Successful attempts have been made by MM. Pieper and Jenatsky to combine the petrol and electric systems, by an arrangement which instead of wasting power in the cylinders when less speed is required, throws into action electric dynamos to store up energy, convertible, when needed, into motive power by reversing the dynamo into a motor. But the simple electric car will not be a universal favourite until either accumulators are so light that a very large store of electricity can be carried without inconvenient addition of weight, or until charging stations are erected all over the country at distances of fifty miles or so apart.

Whether steam will eventually get the upper hand of the petrol engine is at present uncertain. The steam car has the advantage over the gas-engine car in ease of starting, the delicate regulation of power, facility of reversing, absence of vibration, noise and smell, and freedom from complicated gears. On the other hand the petrol car has no boiler to get out of order or burst, no troublesome gauges requiring constant attention, and there is small difficulty about a supply of fuel. Petrol sufficient to give motive power for hundreds of miles can be carried if need be; and as long as there is petrol on board the car is ready for work at a moment’s notice. Judging by the number of the various types of vehicles actually at work we should say that while steam is best for heavy traction, the gas-engine is most often employed on pleasure cars.

D. Liquid Air will also have to be reckoned with as a motive power. At present it is only on its probation; but the writer has good authority for stating that before these words appear in print there will be on the roads a car driven by liquid air, and able to turn off eighty miles in the hour.

Manufacture.—As the English were the pioneers of the steam car, so are the Germans and French the chief manufacturers of the petrol car. While the hands of English manufacturers were tied by shortsighted legislation, continental nations were inventing and controlling valuable patents, so that even now our manufacturers are greatly handicapped. Large numbers of petrol cars are imported annually from France, Germany, and Belgium. Steam cars come chiefly from America and France. The former country sent us nearly 2000 vehicles in 1901. There are signs, however, that English engineers mean to make a determined effort to recover lost ground; and it is satisfactory to learn that in heavy steam vehicles, such as are turned out by Thorneycroft and Co., this country holds the lead. We will hope that in a few years we shall be exporters in turn.

Having glanced at the history and nature of the various types of car, it will be interesting to turn to a consideration of their travelling capacities. As we have seen, a steam omnibus attained, in 1830, a speed of no less than thirty-five miles an hour on what we should call bad roads. It is therefore to be expected that on good modern roads the latest types of car would be able to eclipse the records of seventy years ago. That such has indeed been the case is evident when we examine the performances of cars in races organised as tests of speed. France, with its straight, beautifully-kept, military roads, is the country par excellence for the chauffeur. One has only to glance at the map to see how the main highways conform to Euclid’s dictum that a straight line is the shortest distance between any two points, e.g. between Rouen and Dieppe, where a park of artillery, well posted, could rake the road either way for miles.

The growth of speed in the French races is remarkable. In 1894 the winning car ran at a mean velocity of thirteen miles an hour; in 1895, of fifteen. The year 1898 witnessed a great advance to twenty-three miles, and the next year to thirty miles. But all these speeds paled before that of the Paris to Bordeaux race of 1901, in which the winner, M. Fournier, traversed the distance of 327-1/2 miles at a rate of 53-3/4 miles per hour! The famous Sud express, running between the same cities, and considered the fastest long-distance express in the world, was beaten by a full hour. It is interesting to note that in the same races a motor bicycle, a Werner, weighing 80 lbs. or less, successfully accomplished the course at an average rate of nearly thirty miles an hour. The motor-car, after waiting seventy years, had had its revenge on the railways.

This was not the only occasion on which an express service showed up badly against its nimble rival of the roads. In June, 1901, the French and German authorities forgot old animosities in a common enthusiasm for the automobile, and organised a race between Paris and Berlin. It was to be a big affair, in which the cars of all nations should fight for the speed championship. Every possible precaution was taken to insure the safety of the competitors and the spectators. Flags of various colours and placards marked out the course, which lay through Rheims, Luxembourg, Coblentz, Frankfurt, Eisenach, Leipsic, and Potsdam to the German capital. About fifty towns and large villages were “neutralised”—that is to say, the competitors had to consume a certain time in traversing them. At the entrance to each neutralised zone a “control” was established. As soon as a competitor arrived, he must slow down, and a card on which was written the time of his arrival was handed to a “pilot,” who cycled in front of the car to the other “control” at the farther end of the zone, from which, when the proper time had elapsed, the car was dismissed. Among other rules were: that no car should be pushed or pulled during the race by any one else than the passengers; that at the end of the day only a certain time should be allowed for cleaning and repairs; and that a limited number of persons, varying with the size of the car, should be permitted to handle it during that period.

A small army of automobile club representatives, besides thousands of police and soldiers, were distributed along the course to restrain the crowds of spectators. It was absolutely imperative that for vehicles propelled at a rate of from 50 to 60 miles an hour a clear path should be kept.

At dawn, on July 27th, 109 racing machines assembled at the Fort de Champigny, outside Paris, in readiness to start for Berlin. Just before half-past three, the first competitor received the signal; two minutes later the second; and then at short intervals for three hours the remaining 107, among whom was one lady, Mme. de Gast. At least 20,000 persons were present, even at that early hour, to give the racers a hearty farewell, and demonstrate the interest attaching in France to all things connected with automobilism.

Great excitement prevailed in Paris during the three days of the race. Every few minutes telegrams arrived from posts on the route telling how the competitors fared. The news showed that during the first stage at least a hard fight for the leading place was in progress. The French cracks, Fournier, Charron, De Knyff, Farman, and Girardot pressed hard on Hourgières, No. 2 at the starting-point. Fournier soon secured the lead, and those who remembered his remarkable driving in the Paris-Bordeaux race at once selected him as the winner. Aix-la-Chapelle, 283 miles from Paris and the end of the first stage, was reached in 6 hours 28 minutes. Fournier first, De Knyff second by six minutes.