An electric motor can be turned into an electric generator by simply reversing the direction in which the armature rotates—that is, any electric machine is either a generator or a motor. This fact can be illustrated by means of Figs. 13 and 14, both of which show the armature and the poles of the field magnet. The first figure represents an electric motor, and, as can be seen, the pull between the N pole of the armature and the P pole of the field is in the direction of arrow b, hence the armature will rotate in the same direction, as indicated by arrow a. To obtain the polarity of the armature and field it is necessary to pass an electric current through both—that is to say, we must expend electrical energy to obtain power from the machine. As soon as the current ceases to flow, the polarity of the armature and field dies out, and the rotation of the former comes to an end. The magnetism, however, does not die out entirely; a small residue is always left, although it is never sufficient to produce rotation, and even if it were it could only cause the armature to revolve through one quarter of a turn. If, after the current has been shut off, the armature shaft is rotated in the reverse direction, as indicated by arrow a in Fig. 14, the motion will be against the pull of the magnetism; therefore, although the poles may be very weak, an amount of power sufficient to overcome their attraction must be applied to the pulley, otherwise rotation can not be accomplished. In consequence of the backward rotation a current is generated in the armature coils, and this current, as it traverses the field coils as well as those of the armature, causes the polarity of both parts to increase. As a result of the increased polarity the resistance to rotation is increased, and more power has to be applied to the pulley. The increase in the strength of the poles results in increasing the current generated, and this in turn further increases the pole strength, so that one effect helps the other, the result being that the current, which starts with an infinitesimal strength, soon rises to the maximum capacity of the machine.
The motor shown in Fig. 10 does not in any way resemble an electric railway motor, nevertheless the principle of action is precisely the same in both. The design of a machine of any kind has to conform to the practical requirements, and this is true of railway motors, just as it is true of printing presses, sawmills, or any other mechanism. A railway motor must be designed to run at a comparatively slow speed and to develop a strong rotative force, or torque, as it is technically called. It must also be so constructed that it will not be injured if covered with mud and water. It must be compact, strong, and light, and capable of withstanding a severe strain without giving out. To render the machine water- and mud-proof it is formed with an outer iron shell, which entirely incases the internal parts. The first railway motors were not inclosed, and the result was that they frequently came to grief from the effects of a shower of mud. When the modern inclosed type of motor, which is called the iron-clad type, first made its appearance it was frequently spoken of as the clam-shell type, and the name is not altogether inappropriate, for while the outside may be covered with mud to such an extent as to entirely obliterate the design, the interior will remain perfectly clean and dry, and therefore its effectiveness will not be impaired.
To enable the motor to give a strong torque and run at a slow speed the number of poles in the field and armature is increased. The design of Fig. 10 has two poles in the field and two in the armature, and is what is known as the bipolar type. Machines having more than two poles in each part are called multipolar machines. The number of poles can be increased by pairs, but not by a single pole—that is, we can have four, six, eight, or any other even number of poles, but not five, seven, or any odd number. This is owing to the fact that there must always be as many positive as negative poles, no more and no less. Railway motors at the present time are made with four poles. The external appearance can be understood from Fig. 15, while Fig. 16 and Fig. 17 will serve to elucidate the internal construction. In Fig. 15 the motor casing is marked M, and, as will be seen, it forms a complete shell. The motion of the armature shaft is transmitted to the car-wheel axle F through a pinion, which engages with a spur gear secured to the latter. In Fig. 16 the pinion and gear are marked N and L respectively. As it is necessary that the armature shaft and the axle be kept in perfect alignment, the motor casing M is provided with suitable bearings for both, those for the armature shaft being marked P P in Fig. 16, and one of those for the axle being marked T in Fig. 15. It will be understood from the foregoing that the motor is mounted so as to swing around the car-wheel axle as a center, but, as it is not desirable to have all this dead weight resting upon the wheels without any elasticity, the motor is carried by the crossbars B B, Fig. 15, which rest upon springs s s at each end. The beam A and a similar one at the farther end of the B B bars extend out to the sides of the car truck and are suitably secured to the latter. The coils w w are the ends of the field coils and the armature connections, and to these the wires conveying the current from the trolley are connected. The cover C on top of the motor at one end closes an opening through which access to the commutator brushes is obtained. The armature is shown at H in Fig. 16 and the commutator at K in the same figure. Directly under the armature may be seen one of the field magnet coils, it being marked R.
As will be noticed in Fig. 16, the motor casing is made so as to open along the central line, and the lower half is secured to the top by means of hinges, g g, Fig. 15, and also by a number of bolts, which are not so clearly shown. The gear wheels are also located within a casing, which (Fig. 16) is made so as to be readily opened whenever it becomes necessary. All the vital parts of the machine are entirely covered, and are not easily injured by mud or water.
The construction of the armature and commutator is well illustrated in Fig. 17, which shows this part of the machine by itself. The armature is marked A, the shaft B, and the commutator C. In the diagrams, Figs. 9, 10, 11, and 12, the wire coils are represented as wound upon the surface of the armature core, but, from Fig. 17, it will be noticed that they are located in grooves. A railway motor armature core, when seen without the wire coils, looks very much like a wide-faced cog wheel with extra long teeth, not very well shaped for gear teeth. In Fig. 17 the ends of the teeth are marked D, and the grooves within which the wire is wound are marked E. The coils are not wound so that their sides are on diametrically opposite sides of the armature core, but so that they may be one quarter of the circumference apart, and, as will be noticed, the wires are arranged so as to fit neatly into each other at the ends of the armature core. The bands marked F F F F are provided for the purpose of holding the wire coils within the grooves. The flanges H and I are simply shields to prevent oil, grease, or even water, if it should pass through the bearings, from being thrown upon the commutator or armature. The pinion through which the armature imparts motion to the car-wheel axle is not shown in Fig. 17, but it is mounted upon the taper end of the shaft.
An electric railway motor is a machine that is characterized by extreme simplicity (there being only one moving part), compactness, and great strength. In addition, as none of the working parts is exposed it can not be injured, no matter how much mud may accumulate upon it. One of the reasons why the electric railway motor has met with such unparalleled success is that it is a machine that can withstand the roughest kind of usage without being damaged thereby. Another reason is that an electric motor can, if called upon, develop an amount of power two or three times greater than its full-rated capacity without injury, providing the strain is not maintained too long. A steam engine or any other type of motor that has ever been used for railway propulsion if loaded beyond its capacity will come to a standstill—that is, it will be stalled—but an electric motor can not be stalled with any strain that is likely to be placed upon it. If the load is increased the motor will run slower and the current will become greater, thus increasing the pull, but the armature will continue to rotate until the current becomes so great as to burn out the insulation. A railway motor calculated to work up to twenty-five-horse power will have to develop on an average about six-or seven-horse power, but if the car runs off the track on a steep grade, and has such a heavy load that the motor is called upon to develop one-hundred-horse power for a few seconds, the machine will be equal to the occasion. This result a steam, gas, or any other type of engine can not accomplish, and it is this fact as much as anything else that has given the electric motor the control of the street-railway field.
[To be continued.]
It is during the latter part of the present century that a general movement has arisen to give women their rights in business life and in political and social affairs. It is the intention of this article to treat of this movement, especially in its relation to education, in Germany, where, of all civilized lands, it has had apparently the smallest results. Progress in the direction indicated has been, however, far greater than appears on the surface, and the movement is slowly taking shape in a form that will gain official recognition and support, and the way is being prepared for scholarly attainments among the women of Germany, superior, possibly, to those of the women of other nations.
There is, moreover, an ideal side to this movement in Germany not altogether found in other lands. The motive for advanced study is more largely joy in the study itself, and desire to supply the spiritual needs of an idle life. In order to understand this ideal tendency it is necessary to cast a glance backward over nearly three hundred years.
Let us begin with the contest which was waged so successfully for the development and protection of the German language, first against the Latin and later against the French. In this struggle women took a prominent part, especially through membership in the society called the “Order of the Palms,” which, before the beginning of the Thirty Years’ War, united the strongest spirits of Germany for this purpose. The first woman to join this society was Sophie Elizabeth, Princess of Mecklenburg, married in 1636 to the Herzog of Braunschweig. She was followed by many others, both of the nobility and the common people, and was named by virtue of this leadership “The Deliverer.”
In the eighteenth century we have the founder of the German theater, Caroline Neuber. In the artistic sense she was the first director of the German stage, the first to turn the attention of the greatest actors of her day to the ideal side of dramatic presentation. Early in the eighteenth century women began to take up university studies. A certain Frau von Zingler received a prize from the University of Wittenberg for literary work, and the wife of Professor Gottscheds entered upon a contest for a prize in poetry with her husband.
We find some old verses published in Leipsic, in a book of students’ songs, in 1736, recognizing the fact that women attended lectures in the university there, although the reference is rather sarcastic, speaking of “beauty coming to listen in the halls of learning.”
In 1754 the first woman received her degree of Doctor of Medicine in Halle—Dorothea Christine Erxleben, née Leborin, a daughter of a physician, who attained to this result only after many years of painstaking effort. With her father’s help she studied the classics and medicine, and gradually, in spite of the objections of his brother physicians, began to practice as a doctor under her father’s protection. She is said to have cured her patients cito tuto, jucunde, and in 1742 she published a book on the right of women to study, the title of which, according to the custom of the day, included the full table of contents. This book passed through two editions, and enabled her to gain the attention of Frederick II, who was persuaded to order the University of Halle to grant her the privilege of taking her examination there. The day arrived, and the hall was crowded for the occasion; the candidate passed the ordeal in a brilliant manner, and took the oath for the doctor’s degree amid a storm of applause from the listeners present.
In the present century the germ of the movement for educational rights for women came into consciousness in Germany in the stormy year 1848, and first found expression and life through the work of two women—Louise Otto Peters and Auguste Schmidt. The former founded the Universal Association for Women in Germany, and through this society both these women worked for thirty years and did much toward preparing the way for the broader efforts of the present time.
It is a fact granted by all the educational world that scholarship attains a depth and thoroughness in Germany not found in other lands, and this very perfection has been in part the cause of the backwardness of the educational movement among the women, for a high degree of scholarship has often been acquired by the men at the expense of the devoted service of the women connected with them. Yet when the women of Germany demand their educational rights it will be to share also in the rich intellectual inheritance of their land.
The majority of the men thus far regard the movement with distrust and suspicion, but are powerless to crush it out. An amusing instance occurred last year in the family of an official in one of the large university towns. He was a conservative man who had his immediate family in a proper state of subjection, but his mother-in-law, alas! he could not control, and to his dismay she enrolled herself at the university as a Hospitant, and, in spite of the protestations of her son-in-law, she was a regular attendant upon the courses of lectures that she had elected.
The regular schools for girls in Germany, above the common schools attended by girls and boys together, are of two grades—the middle schools and the high schools. The avowed object of these schools is to fit girls for society and for the position of housewife, as Herr Dr. Bosse, the Minister of Public Instruction for the German Empire, states in his report on the condition of girls’ schools in Germany, and as he publicly declared before the German Parliament in the discussion regarding the establishment of a girls’ gymnasium in Breslau, referred to later on in this paper.
The girls’ schools established by the Government provide well for the study of the modern languages, and it is the exception to find women in the upper classes who do not speak French and English. Literature, religion, gymnastics, and needlework are also well taught. The course of study in the high school includes a little mathematics, offered under the name of reckoning, and sufficient to enable a woman to keep the accounts of a household, and also a little science of the kind that can be learned without a knowledge of mathematics. Let me quote a paragraph from the report of the Minister of Public Instruction for the year 1898 in regard to the aim of the mathematical course in the girls’ high schools: “Accuracy in reckoning with numbers and the ability to use numbers in the common relations of life, especially in housekeeping. Great weight is laid upon quick mental computations, but in all grades the choice of problems should be such as especially apply to the keeping of a house.” This is the opportunity which is offered to girls by the Government in the department of mathematics! In addition to the two grades of schools mentioned there are seminaries in many of the large cities for the purpose of educating women teachers. The instructors in these seminaries are well prepared for their positions, are mostly men, and the instruction given is very superior to that given in the girls’ high schools. Latin and Greek are, however, not studied in these seminaries, and mathematics and science are expurgated, we might say, of points that might prove difficult for the feminine intellect.
The ability to learn Latin and Greek seems in the German mind to especially mark the dividing line between the masculine and feminine brain. The writer was at one time studying a subject in Greek philosophy, in the City Library of Munich, requiring the use of a number of Greek and Latin books, and it was amusing to notice the astonishment of the men present that a woman should know the classic languages!
The women who hold certificates from the seminaries are allowed, according to a new law passed in 1894, to continue their studies and to take the higher teachers’ examinations. This is considered a great step in advance, for a woman who has successfully passed this latter examination can hold any position in the girls’ schools, and can even be director of such a school.
That German women have long been discontented with the education provided for them by the Government is proved by the fact that the number of higher institutions offering private opportunities to girls is constantly increasing. As far back as 1868 the Victoria Lyceum was founded by a Scotch woman—Miss Georgina Archer—at her own expense and on her own responsibility, and this institution was well sustained from the beginning. It is now under the patronage of the Empress Frederick, and offers courses to women that run parallel to a certain extent with those given on the same subjects in the university. Professors from the university lecture in the Victoria Lyceum, but a young woman who had listened to the same professor in both places informed me that he (perhaps unconsciously) simplified his lectures very much for the Victoria Lyceum. Fraulein Anna von Cotta is the director of the institution. Among the women who teach there we note the name of the well-known Fraulein Lange, who lectures on psychology and German literature.
There are several girls’ gymnasia in Germany which testify to the demand for higher education. These institutions are all but one private, and three of them—one in Leipsic, one in Berlin, and a third, opened in October, 1898, in Königsberg—are called “gymnasial courses,” and are for girls who have finished the girls’ high school, and who must pass entrance examinations in order to be received into them.
There has been for some time a girls’ gymnasium which corresponds exactly to those for boys in Carlsruhe, under the auspices of the “Society for Reform in the Education of Women,” which receives girls of twelve who must have finished the six lower classes of a girls’ school. This society, to which the girls of Germany owe much, is planning to open another gymnasium in Hannover, to which girls will be received from the junior class of the girls’ high school; the course of study will occupy five years, and will fit girls for the same official examinations as the boys’ gymnasia. The language courses in the highest class will be elective, providing either for Greek or the modern languages, but Latin is obligatory in all the classes. The girls from all these gymnasia are debarred from taking any of the official examinations for which their studies have prepared them.
The next step in the matter of gymnasial education for girls was what might have been expected. The people of the wide-awake city of Breslau voted, by an overwhelming majority, to establish a girls’ gymnasium under the same laws and furnishing the same advantages as the boys’ gymnasia. The completed plan was sent to the Minister of Public Instruction in Berlin in January, 1898, for approval, with the intention of opening the gymnasium at Easter, for which twenty-six girls were already enrolled. Herr Dr. Bosse, however, foreseeing the results such an undertaking would involve, consulted the other departments of the ministry, and two months later a decided refusal came like a thunderbolt upon the people of Breslau. On the 30th of April, 1898, Herr Dr. Bosse was called to account in the Reichstag for his action in the matter, which he justified on the ground that Government approval of girls’ gymnasia would mean the acceptance of the diploma for matriculation in the universities and the opening to women of all Government professional examinations, and that to have granted it would have been to take a step in the direction of the modern movement for women which could never have been recalled, and would open the lecture rooms of Germany in general to women. He contended, further, that the founding of official gymnasia for girls would delegate the existing girls’ high school to a secondary place, an institution which had been planned thoughtfully by the Government for the purpose of educating women in the best manner, not to become rivals of men, but help-meets and able housekeepers.
The demand of the people of Breslau, Dr. Bosse said, was an unnatural one, and his refusal was founded on the fear that such a movement would increase and threaten the social foundations of all Germany, as the idea that women can compete with men in all careers is a false one.
The petition of the magistrate of Breslau was supported in the discussion by some of the national-liberal, free-conservative, and Polish representatives. These took the broad ground that girls have a right to equal education with boys, and that the educational institutions of Germany which have so long stood at the head of those of the world should not, in the matter of education of women, leave the question to be decided according to the whims of private individuals.
Some of the arguments of those who spoke in favor of the enterprise were amusing. One said that the girls of Germany would be grateful if the Minister of Public Instruction would furnish them with husbands, but, as there were not enough to go around, the others should have some career provided for them. Another, that about forty per cent of the girls of the higher classes no longer marry, and they should not be allowed to suffer the consequences of the fact that young men of the present day do not care to marry, but they have a right that the way be shown them to such careers as are suited to their feminine nature.
An objector said that he could not understand how any man of pedagogical culture could approve of a girls’ gymnasium, for it is evident that any such progress for women as that would imply must be at the expense of the men, who would gain less on account of the increased number of candidates for work of all kinds and would more seldom be able to offer the best of all existences to a woman—that of wifehood. The city of Breslau was obliged, therefore, to give up the undertaking for the present, but the agitation of the question has probably prepared the way for more extended plans in the future in the same direction in Prussia.
A similar undertaking in Carlsruhe, in Baden, has met with better success, and resulted in the opening of the first official gymnasium for girls in Germany, in September, 1898. This gymnasium was planned about the same time as that of Breslau, and as the permission of the Minister of Public Instruction in Baden was obtained without difficulty, the institution came into existence according to the will of the people of Carlsruhe. Seventy-nine of the members of the Bürgerauschuss voted in favor of the undertaking in the meeting in which the final action was taken early in the summer of 1898. The Christian-conservative party only decidedly opposed it. The leader of this party was very much excited over the matter, and called out, when the action was taken, “I ask you, gentlemen, on your honor, if any of you would marry a girl from a gymnasium?”
The opening of the Government gymnasium will remove the necessity for continuing the private one in Carlsruhe, under the society in charge of it, and leave that society free to direct its efforts elsewhere.
There had already been several references to the general subject of the education of women in the Reichstag before the question of the gymnasium in Breslau came up. In January, 1898, Prince Carolath spoke in favor of founding several girls’ gymnasia, and admitting women legally to the universities and to pedagogical and to medical state professional examinations, remarking that in all other civilized lands the universities are more open to women than in Germany.
Coming now to the present attitude of the universities to the higher education of women, we find that a great change has taken place during the last few years. While it is still the fact that no German woman can matriculate in any university in Germany, yet the problem of the stand which the universities should take is working out its own solution in the right direction.
The University of Berlin, the largest and in many respects the leading one, has made progress in the matter, although women still work there under great limitations. The cause was injured at the outset in Berlin by the fact that women, often foreigners, who had not the required preparation, rushed into lecture rooms which were open to them from motives of curiosity. This caused such strong feeling among the professors that in one instance a professor, on entering his classroom, saw a lady sitting in the rear, walked up to her, offered her his arm, and led her out of the room.
The first step in the right direction has been to demand either a diploma from some well-known institution, or, as that could not be complied with by German women, the certificate of the teachers’ examinations. The possessors of such credentials may attend lectures in any course, where the professor is willing, as Hospitants. The conditions under which women may attend the University of Berlin are the following:
1. A written permission must be obtained from the curator of the university on presentation of a satisfactory diploma, a passport, and, by Russian applicants, a written permission from the police authorities to study in Germany.
2. Written permission from the rector.
3. Written permission from the professors or docents whose lectures the applicant wishes to attend.
4. The permission from the rector must be obtained each semester, but from the curator only when a new subject is chosen.
5. The same fee is demanded from women as from men, and women are requested to always carry with them, in attending lectures, the written permission from the rector.
At the public installation of Rector Waldeyer, in October, 1898, both in his address and in that of the resigning rector, Geheimrath Professor Schmoller, the subject of education of women received attention.
Geheimrath Schmoller said that the first condition of further concessions in the matter must be better preparation on the part of the women, and when this deficiency should be provided for the faculty of the university could make the conditions of their attending lectures lighter, perhaps even the same as those for men. Geheimrath Waldeyer made the subject one of three to which he gave equal space, and which he said called for immediate attention in the educational affairs of Germany. The other two subjects were the relation of technical schools to the universities, and university extension. Geheimrath Waldeyer said that he had formerly been opposed to the higher education of women, but had been led to change his mind from seeing that the movement is not an artificial one, but rather the natural result of the present social condition of society, and on the simple ground of right should be forwarded in a legitimate manner. He spoke strongly, however, in favor of the establishment of separate universities for men and women, on account of the natural differences in the working of their minds and the necessity of adapting methods in both instances to their needs.
The number of women in the University of Berlin has increased very rapidly, being in the autumn of 1896 thirty-nine, in the winter of the same year ninety-five. The next year the largest number was nearly two hundred, and in 1897–’98 three hundred and fifty-two were in all inscribed. Nearly half of these were German women. Most of the women in the University of Berlin are in the department of philosophy, but several are pursuing courses in theology and law. These women are of all ages. One from Charlottenburg was sixty-two years old, and, besides this honored lady, there were five others whose white hair testified to an age of from fifty to fifty-five, while the youngest of all was a Bulgarian girl of seventeen.
The first woman to take her degree in the University of Berlin was Dr. Else Neumann, in December, 1898, in physics and mathematics, who succeeded, notwithstanding the difficulties to be contended with in the absence of preparatory study and the necessity for private preparation.
It is not, however, only in Berlin that the desire for university study has taken a strong hold on the German women, but it is shown in other places, not simply by the fact that many of them attend the universities of Switzerland, which are everywhere open to them, but by their also obtaining the advantages in their own land which have so long been denied them.
Heidelberg was the first university in Germany to grant the doctor examination to women, and this was done several years before lectures were open to them. The writer called upon Prof. Kuno Fischer one day in the summer of 1890 to ask permission to attend a lecture which he was to give that afternoon on Helmholtz. He said that he was very sorry indeed, but he was obliged to refuse women the privilege of listening to him, as they were not admitted to the university. I asked when they would probably be admitted, and he replied, speaking in French, “Jamais, mademoiselle, jamais!” Four years later, however, a friend of mine took her degree there in the department of philosophy, thus proving that the wisest of men sometimes make mistakes.
Women have for years studied as Hospitants in the Universities of Leipsic and Göttingen, but since November, 1897, the conditions of their admission in Göttingen have been made more difficult.
In Kiel the professors who are not willing to allow women to attend their lectures put a star opposite their names in the university programme of the lecture courses, and this star is unfortunately seen opposite the names of all the professors of theology and many of those of medicine. Women began to attend the University of Tübingen in the autumn of 1898, Dr. Maria Gräfin von Linden being the first, who was soon followed by many others.
The degree of Doctor of Philosophy honoris causa has been conferred on two women by the University of Munich—in December, 1897, on the Princess Theresa, and in October, 1898, on Lady Blennerhassett, an author, for her researches in modern languages. The Dean of the Philosophical Faculty, accompanied by three professors, visited her in her home in Munich to communicate to her the honor which she had received.
The University of Breslau offers better conditions to women than are provided elsewhere, as might naturally be expected, especially in the department of medicine.
Germany was represented in the International Council of Women, held in London in June of this present year, by Frau Anna Simson, Frau Bieber Boehm, and Fran Marie Stritt, of Dresden.
It was also decided at this congress that the next Quinquennial International Council of Women should be held in Berlin, and it will without doubt be an occasion that will mark an era in the history of the progress of liberty for the women of Germany.
Although amateurs have played a conspicuous part in telescopic discovery among the heavenly bodies, yet every owner of a small telescope should not expect to attach his name to a star. But he certainly can do something perhaps more useful to himself and his friends. He can follow the discoveries that others, with better appliances and opportunities, have made, and can thus impart to those discoveries that sense of reality which only comes from seeing things with one’s own eyes. There are hundreds of things continually referred to in books and writings on astronomy which have but a misty and uncertain significance for the mere reader, but which he can easily verify for himself with the aid of a telescope of four or five inches’ aperture, and which, when actually confronted by the senses, assume a meaning, a beauty, and an importance that would otherwise entirely have escaped him. Henceforth every allusion to the objects he has seen is eloquent with intelligence and suggestion.
Take, for instance, the planets that have been the subject of so many observations and speculations of late years—Mars, Jupiter, Saturn, Venus. For the ordinary reader much that is said about them makes very little impression upon his mind, and is almost unintelligible. He reads of the “snow patches” on Mars, but unless he has actually seen the whitened poles of that planet he can form no clear image in his mind of what is meant. So the “belts of Jupiter” is a confusing and misleading phrase for almost everybody except the astronomer, and the rings of Saturn are beyond comprehension unless they have actually been seen.
It is true that pictures and photographs partially supply the place of observation, but by no means so successfully as many imagine. The most realistic drawings and the sharpest photographs in astronomy are those of the moon, yet I think nobody would maintain that any picture in existence is capable of imparting a really satisfactory visual impression of the appearance of the lunar globe. Nobody who has not seen the moon with a telescope—it need not be a large one—can form a correct and definite idea of what the moon is like.
The satisfaction of viewing with one’s own eyes some of the things the astronomers write and talk about is very great, and the illumination that comes from such viewing is equally great. Just as in foreign travel the actual seeing of a famous city, a great gallery filled with masterpieces, or a battlefield where decisive issues have been fought out illuminates, for the traveler’s mind, the events of history, the criticisms of artists, and the occurrences of contemporary life in foreign lands, so an acquaintance with the sights of the heavens gives a grasp on astronomical problems that can not be acquired in any other way. The person who has been in Rome, though he may be no archæologist, gets a far more vivid conception of a new discovery in the Forum than does the reader who has never seen the city of the Seven Hills; and the amateur who has looked at Jupiter with a telescope, though he may be no astronomer, finds that the announcement of some change among the wonderful belts of that cloudy planet has for him a meaning and an interest in which the ordinary reader can not share.
Jupiter is perhaps the easiest of all the planets for the amateur observer. A three-inch telescope gives beautiful views of the great planet, although a four-inch or a five-inch is of course better. But there is no necessity for going beyond six inches’ aperture in any case. For myself, I think I should care for nothing better than my five-inch of fifty-two inches’ focal distance. With such a glass more details are visible in the dark belts and along the bright equatorial girdle than can be correctly represented in a sketch before the rotation of the planet has altered their aspect, while the shadows of the satellites thrown upon the broad disk, and the satellites themselves when in transit, can be seen sometimes with exquisite clearness. The contrasting colors of various parts of the disk are also easily studied with a glass of four or five inches’ aperture.
There is a charm about the great planet when he rides high in a clear evening sky, lording it over the fixed stars with his serene, unflickering luminousness, which no possessor of a telescope can resist. You turn the glass upon him and he floats into the field of view, with his cortége of satellites, like a yellow-and-red moon, attended by four miniatures of itself. You instantly comprehend Jupiter’s mastery over his satellites—their allegiance is evident. No one would for an instant mistake them for stars accidentally seen in the same field of view. Although it requires a very large telescope to magnify their disks to measurable dimensions, yet the smallest glass differentiates them at once from the fixed stars. There is something almost startling in their appearance of companionship with the huge planet—this sudden verification to your eyes of the laws of gravitation and of central forces. It is easy, while looking at Jupiter amid his family, to understand the consternation of the churchmen when Galileo’s telescope revealed that miniature of the solar system, and it is gratifying to gaze upon one of the first battle grounds whereon science gained a decisive victory for truth.
The swift changing of place among the satellites, as well as the rapidity of Jupiter’s axial rotation, give the attraction of visible movement to the Jovian spectacle. The planet rotates in four or five minutes less than ten hours—in other words, it makes two turns and four tenths of a third turn while the earth is turning once upon its axis. A point on Jupiter’s equator moves about twenty-seven thousand miles, or considerably more than the entire circumference of the earth, in a single hour. The effect of this motion is clearly perceptible to the observer with a telescope on account of the diversified markings and colors of the moving disk, and to watch it is one of the greatest pleasures that the telescope affords.
It would be possible, when the planet is favorably situated, to witness an entire rotation of Jupiter in the course of one night, but the beginning and end of the observation would be more or less interfered with by the effects of low altitude, to say nothing of the tedium of so long a vigil. But by looking at the planet for an hour at a time in the course of a few nights every side of it will have been presented to view. Suppose the first observation is made between nine and ten o’clock on any night which may have been selected. Then on the following night between ten and eleven o’clock Jupiter will have made two and a half turns upon his axis, and the side diametrically opposite to that seen on the first night will be visible. On the third night between eleven and twelve o’clock Jupiter will have performed five complete rotations, and the side originally viewed will be visible again.
Owing to the rotundity of the planet, only the central part of the disk is sharply defined, and markings which can be easily seen when centrally located become indistinct or disappear altogether when near the limb. Approach to the edge of the disk also causes a foreshortening which sometimes entirely alters the aspect of a marking. It is advisable, therefore, to confine the attention mainly to the middle of the disk. As time passes, clearly defined markings on or between the cloudy belts will be seen to approach the western edge of the disk, gradually losing their distinctness and altering their appearance, while from the region of indistinct definition near the eastern edge other markings slowly emerge and advance toward the center, becoming sharper in outline and more clearly defined in color as they swing into view.
Watching these changes, the observer is carried away by the reflection that he actually sees the turning of another distant world upon its axis of rotation, just as he might view the revolving earth from a standpoint on the moon. Belts of reddish clouds, many thousands of miles across, are stretched along on each side of the equator of the great planet he is watching; the equatorial belt itself, brilliantly lemon-hued, or sometimes ruddy, is diversified with white globular and balloon-shaped masses, which almost recall the appearance of summer cloud domes hanging over a terrestrial landscape, while toward the poles shadowy expanses of gradually deepening blue or blue-gray suggest the comparative coolness of those regions which lie always under a low sun.
After a few nights’ observation even the veriest amateur finds himself recognizing certain shapes or appearances—a narrow dark belt running slopingly across the equator from one of the main cloud zones to the other, or a rift in one of the colored bands, or a rotund white mass apparently floating above the equator, or a broad scallop in the edge of a belt like that near the site of the celebrated “red spot,” whose changes of color and aspect since its first appearance in 1878, together with the light it has thrown on the constitution of Jupiter’s disk, have all but created a new Jovian literature, so thoroughly and so frequently have they been discussed.
And, having noticed these recurring features, the observer will begin to note their relations to one another, and will thus be led to observe that some of them gradually drift apart, while others drift nearer; and after a time, without any aid from books or hints from observatories, he will discover for himself that there is a law governing the movements on Jupiter’s disk. Upon the whole he will find that the swiftest motions are near the equator, and the slowest near the poles, although, if he is persistent and has a good eye and a good instrument, he will note exceptions to this rule, probably arising, as Professor Hough suggests, from differences of altitude in Jupiter’s atmosphere. Finally, he will conclude that the colossal globe before him is, exteriorly at least, a vast ball of clouds and vapors, subject to tremendous vicissitudes, possibly intensely heated, and altogether different in its physical constitution, although made up of similar elements, from the earth. Then, if he chooses, he can sail off into the delightful cloud-land of astronomical speculation, and make of the striped and spotted sphere of Jove just such a world as may please his fancy—for a world of some kind it certainly is.
For many observers the satellites of Jupiter possess even greater attractions than the gigantic ball itself. As I have already remarked, their movements are very noticeable and lend a wonderful animation to the scene. Although they bear classical names, they are almost universally referred to by their Roman numbers, beginning with the innermost, whose symbol is I, and running outward in regular order II, III, and IV. The minute satellite much nearer to the planet than any of the others, which Mr. Barnard discovered with the Lick telescope in 1892, is called the fifth, although in the order of distance it would be the first. In size and importance, however, it can not rank with its comparatively gigantic brothers. Of course, no amateur’s telescope can show the faintest glimpse of it.
Satellite I, situated at a mean distance of 261,000 miles from Jupiter’s center—about 22,000 miles farther than the moon is from the earth—is urged by its master’s overpowering attraction to a speed of 320 miles per minute, so that it performs a complete revolution in about forty-two hours and a half. The others, of course, move more slowly, but even the most distant performs its revolution in several hours less than sixteen days. The plane of their orbits is presented edgewise toward the earth, from which it follows that they appear to move back and forth nearly in straight lines, some apparently approaching the planet, while others are receding from it. The changes in their relative positions, which can be detected from hour to hour, are very striking night after night, and lead to a great variety of arrangements always pleasing to the eye.
The most interesting phenomena that they present are their transits and those of their round, black shadows across the face of the planet; their eclipses by the planet’s shadow, when they disappear and afterward reappear with astonishing suddenness; and their occultations by the globe of Jupiter. Upon the whole, the most interesting thing for the amateur to watch is the passage of the shadows across Jupiter. The distinctness with which they can be seen when the air is steady is likely to surprise, as it is certain to delight, the observer. When it falls upon a light part of the disk the shadow of a satellite is as black and sharply outlined as a drop of ink; on a dark-colored belt it can not so easily be seen.
It is more difficult to see the satellites themselves in transit. There appears to be some difference among them as to visibility in such circumstances. Owing to their luminosity they are best seen when they have a dark belt for a background, and are least easily visible when they appear against a bright portion of the planet. Every observer should provide himself with a copy of the American Ephemeris for the current year, wherein he will find all the information needed to enable him to identify the various satellites and to predict, by turning Washington mean time into his own local time, the various phenomena of the transits and eclipses.
While a faithful study of the phenomena of Jupiter is likely to lead the student to the conclusion that the greatest planet in our system is not a suitable abode for life, yet the problem of its future, always fascinating to the imagination, is open; and whosoever may be disposed to record his observations in a systematic manner may at least hope to render aid in the solution of that problem.