as that of the meteor shower of 1872-between Perseus, Cassiopea, and Andromeda. No secondary centre of radiation was seen, as ordinarily is the case on the nights of greater displays."

All this stellar pyrotechny is of great importance in the eyes of the astronomer, for it brings to his mind fresh proof of the correctness of the theory connecting these displays with comets. These latter wanderers are frequent visitors in that portion of space where the Divine Hand has traced the pathway of our little earth. Even at present there are two, nightly visible in the telescope-Barnard's comet, and one discovered at Paris on December 1st, 1885, by Fabry. According to Dr. Oppenheim (Paris) they will be distinctly visible to the naked eye in northern latitudes about the middle of April or the first of May. Now, some of these comets that cross the earth's orbit are supposed to throw off large masses of matter. This matter may be in the state of gas, or may be a collection of finely divided particles of a solid substance. It is immaterial for our purpose which-it is enough for us that it separates into a number of small bodies revolving in the same orbit as when they were a part of the original mass. The earth as it wheels around its orbit will at some point cross the pathway of the comet. Let us suppose that these stray pieces of the comet are dashing past the crossing point at the same time; they will then come in contact with our atmosphere. Before this contact they are invisible by reason of their smallness, but upon entering our atmosphere they rub against the particles of the air-an enormous heat is generated-the pieces of the comet become brilliantly lighted up-a bright star shoots across the sky. If they are small they vaporize at once, and disappear forever. If they are large enough, or of such a matter as to withstand the heat generated by their motion through the air, they drop to the earth as aerolites. If on any particular occasion they break forth in great numbers from one point of the heavens, we have a star-shower, such as was witnessed on November 27th.

On this theory can be readily explained the brilliant meteoric displays of November 12th-13th. After a long series of investigations by Professor Newton of Yale, and others, it was concluded that they were caused by the earth's encountering a swarm of meteoroids following in the wake of a telescopic comet discovered by Tempel at Marseilles in December, 1865. A similar connection was shown by Schiaparelli to exist between the August meteor-showers and the second comet of 1862. In the case before us we have a further and very striking proof of this connection. But with what comet are we to connect these meteors of November 27th? The astronomer, searching through the history of heavenly bodies, answers at once-with Biela's comet. What are the reasons that lead him to this conclusion? Let us first say a word or two in regard to the history of this comet. Taking its name from Biela, an Austrian astronomer, who was the first to calculate its orbit, in 1826, it was found to have been observed in 1805, and earlier still in 1772. Its period of revolution was fixed at about six years and six months. However, its next observed visit to the region of the earth was delayed till

It

In

the November of 1845. In the following January it was found to have suffered an accident unheard of in the history of its brother comets. split into two unequal parts, and thus divided sailed off into space. 1852 it showed itself again, but about September of that year disappeared. Since then eager astronomers have kept up the watch for it during each of its returning periods. It has never reappeared, but on the night of November 27th, 1872, and again during last November, a remarkable stream of meteors was found wandering around the deserted orbit of the comet. Here, then, we build up our reasons for asserting the connection of this star-shower with Biela's comet. First, this stream of meteors exhibits a perfect orbital resemblance to the comet; secondly, the time of the occurrence of this shower is found to be exactly that in which the earth is at the crossing-point of the two orbits, and it is witnessed only in those years when, according to computation, the comet should be somewhere in the vicinity of this crossing-point; and lastly, the radiant point in Andromeda from which the meteors diverge corresponds most accurately to that from which fragments of the comet, moving in the orbit of the original mass, would seem to come. All this can scarcely be the result of mere chance, and weighing well the many facts presented to us, we can reasonably conclude, though not with absolute certainty, that these splendid meteoric displays of November 27th are caused by the burning in the earth's atmosphere of a swarm of meteoroids-remnants of the departed glory of Biela's comet.

CELESTIAL PHOTOGRAPHY.

When, in 1840, Dr. Draper, of New York, succeeded in photographing the Moon, few astronomers even suspected that before the century's close the camera would play such an important rôle in the observatory. In the "Month" for last December Rev. Fr. Perry, S. J., with his wonted thoroughness, gives a view of the camera's applications, past and present, in the celestial science. But so rapid is the progress, and so widespread the good results obtained in this line, that since the publication of Fr. Perry's article some very important achievements have been made public. Among these is the discovery by photography of a new nebula in the Pleiades.

The new nebula, as first photographed on November 16th by MM. Henry at Paris, has a very well marked spiral form, and seems just to escape Maia. Since then it has been photographed several times, but only very lately has it been seen with the great Pulkowa Refractor; and thus we have another instance proving, as had already been done for the stars, that light can fix on a photographic plate the images of objects which can scarcely be seen, even with the largest telescopes. Nor is this the only advantage of photography when applied to the nebulæ. It is chiefly valuable for its detailed accuracy in furnishing the only trustworthy criterion of change in those strange bodies. For, as all know, it is especially in the details that artists fail in reproducing the exact shape of the nebulæ. Even the least source of information regarding VOL. XI.-24

their forms is welcome, as they constitute so important a link in La Place's theory.

In the November meeting of our Academy of Science at Albany, Prof. E. C. Pickering, referring to the recent progress in celestial photography, made the following remarks: "The first stellar photographs ever taken were those of a Lyræ, by the elder Bond at the Harvard Observatory in 1850. In 1857 his son carried similar investigations much further. At first they had been unable to obtain clear images of stars of the second magnitude, while now it is possible to print those of the fourteenth, or, in other words, to transfer to paper an image produced by an object only a hundred-thousandth part as bright as formerly." He then goes on to expose the three different fields of investigation opened-first, that of mapping the heavens; second, that of studying stellar spectra; and finally, the determination of the amount of atmospheric absorption.

With regard to the first of these points, we may remark that a project is already on foot to obtain the co-operation of astronomers of different nations, many of whom are interested in this new work. They should all follow the same method, and portion out among themselves the heavens. One of Professor Pickering's aims is to further this project, so that before the close of the 19th century we may have a map of the universe with stars down to the fourteenth magnitude, all stamped in their true relative position. This, indeed, would be an arduous undertaking, and utterly to be despaired of did we rely on the artist, for the labor of an hour by the new process would cost the draughtsman months of toil.

The foregoing presents but a small portion of the work done by astronomic photography, in which great progress has been made during the past few years. Want of space prevents us from dwelling at present upon other applications of the same process, to the determination of the connection between magnetic storms and the sun-spots and faculæ; to the reproduction of the exact appearance of the planets, especially of Venus at the moment of its transits, and to the mapping of the linesthe Fraunhofer lines-of the solar spectrum, which has been so successfully and exactly done by the Rowland's gratings. We may return to this subject at an early opportunity.

PHYSICS.
ELECTRICITY.

Of the many recent discoveries and researches made in this everincreasing branch of science we will mention a few of more general interest.

As stated in most daily papers, Mr. Edison has very lately made, on the Staten Island Railway, several successful experiments of his system of inductive telegraphy. The idea is not new. A few years ago similar

successful attempts were made on the New York Central Railway with the Phelps system. This system, however, requires a specially laid wire between the tracks, while Mr. Edison uses the ordinary telegraph wires stretched along the road. We shall endeavor to explain, even without diagrams, the Edison method. The apparatus used, both on the train and at the fixed stations, consists of an ordinary Morse key, a vibrating reed, an induction coil and a battery, for sending the dispatches; and, for receiving them, of a phonetic receiver or telephone. The principle involved in this method is that of electric influence or induction. Whenever a current begins or ceases to traverse a wire, it produces an instantaneous current in a neighboring wire. This action is called induction. It is well known that if the telephone wires are strung close to the telegraph wires, the dispatches passing through the latter can be more or less easily heard. This fact, which in ordinary cases is an inconvenience, is ingeniously utilized by Edison in his new system for receiving dispatches, while similar currents are made use of for sending them. Suppose a dispatch is to be sent. The two extremities of the secondary wire of the induction coil are respectively connected, one with the ground through the car-wheels, the other with the tin roof of all the cars of the train. In the circuit of the primary wire with the battery the Morse key is introduced, and also a vibrating reed, which is made to vibrate five hundred times a second by means of a small independent battery. The ordinary Morse alphabet is used. When the operator lowers the key, not one but many interrupted discharges pass through the primary wire. These are reproduced in the secondary wire, and are changed into currents of high tension, or potential, as they are technically called. These currents pass unto the car roofs, from which they affect the telegraph wires stretched along the road. If a phonetic receiver or telephone is interposed in the circuit of the line wire, an operator, at any fixed station, perceives the dots and dashes produced by the key on the train that sends the telegram.

At the fixed stations a similar apparatus sends induction-currents on the telegraph wires; the high potential currents passing through them affect the roofs of the moving cars. The induction currents communicated to the tin roofs pass through a phonetic receiver or telephone, and thus enable the operator on the car to perceive the dots and dashes of the key that transmits the message.

The system, which has been successfully tried, is on the point of being introduced on some railroads. As its expenses are very small, and its usefulness recognized on all sides, it will perhaps be adopted by most of the railroads of the country.

We take pleasure in announcing the fact that Mr. J. A. Maloney, of Washington, D. C., has quite recently patented a reversible telegraph key. There can be no doubt that this key, when more generally known, will prove to be of the greatest utility to telegraph operators. According to the method heretofore made use of, the operators when obliged to work for hours in succession oftentimes endured extreme fatigue, and not unfrequently became afflicted with what is called "operator's paralysis,"

brought about by the constant up and down motion of the hand pressed upon the key whilst sending the message. Now the very ingenious contrivance of Mr. Maloney has for its purpose to remedy this evil. In Mr. Maloney's invention, by a simple arrangement of a screw, the operator may in a few seconds cause the key to play from side to side, instead of the up and down movement. This change has proved to be a very great relief, so much so that persons already afflicted with the paralysis are enabled, by using this system, to continue their occupation. In a test case to which the recent invention was subjected, it was found that a person very badly afflicted with this paralysis, and who in the ordinary way could work the key but for a very few moments, was able to use the reversed one for hours without experiencing the slightest inconvenience.

Lately two authoritative reports have fallen into our hands which seem to settle that very practical question as to the relative merits and advantages of the electric light and other methods of illumination. Knowing as we do how often persons desirous of informing themselves on this subject are confronted with very questionable statements of parties interested in the one method or the other, we feel all the more inclined to place before our readers a summary of these reports, deeming them worthy of all reliance.

The recent experiment of the Franklin Institute upon incandescent and arc-lights, gives the following averages: one pound of anthracite, burned under a good boiler, yields in the incandescent system of lighting about 40 candles for an hour; the same weight of coal gives from the naked arc-light about 158 candles; as, however, the arc-lights are generally shaded, the intensity is so far diminished that it scarcely reaches 80 candles per pound. One pound of bituminous coal will yield from 5 to 6 feet of illuminating gas. This gas, in the argand burner, will yield from 14 to 17 candles. Illuminating gas is burned at once in the simplest manner, and the amount of machinery and care required by electric lighting offsets its greatest economy of fuel, light for light.

From the report of Trinity House, in England, on the inquiry into the relative merits of electricity, gas, and oil, the general conclusions arrived at by the committee were these: that the "electric light, as exhibited in the experimental tower of South Foreland, has proved to be the most powerful light under all conditions of weather, and to have the greatest penetrative power in fog"; and that for all practical purposes the gas and oil were equal. "For the ordinary necessities of light-house illumination mineral oil is the most suitable and economical illuminant, and that for salient headlands, important land-falls, and places where a very powerful light is required, electricity offers the greatest advantages."