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sively on to the various bands for relative measures ; for comparative measures it is necessary that the telescope should be provided with a good finder. For determining the position of the lines, the star is placed behind one of the threads of the finder; the spectrometer of the large telescope is so placed that the lines in the spectrum are parallel to the celestial equator or to the diurnal motion of the stars; then one of the moveable points of the micrometer is brought on to the most prominent line of the star under examination—such, e.g., as of a Lyræ.
The relative position of the two telescopes is then left untouched, and without moving the micrometer screw, the other star, of which it is desired to know whether the line is or not identical with that of the comparison star, is placed under the same thread of the finder. If the spectral line coincides under the point of the micrometer, as also in the other star, it is evident that the two lines have the identical degree of refrangibility, and are alike.
Comparison stars can easily be selected with a view to the comparison of as many others as is desired, as there are always visible, at all seasons, some well-known coloured stars, as a Orionis, B Pegasi, Antares, a Herculis, &c., which give numerous very distinct lines, and white lines of the type of a Lyræ and of Sirius are very frequent. Since these stars are bright enough to enable the determination of the position of their lines with ordinary spectrometers with a slit in comparison with the sun, so by means of these stars the relative refrangibility of all the other lines may be known.
Such is the very simple spectrometer that I have constructed for the stars. The light which it leaves is such that well-defined spectra may be obtained from stars of the sixth magnitude, and it may be ascertained whether there are black spaces in them, and of what type they are. By applying it to a finder of 45 m.m.
inches) in aperture, I have seen clearly the lines of a Aquilæ. Professor Respighi has been able to see and to separate the bands of Antares with his refractor of 5 inches. Thus amateurs can, with moderate instruments, henceforth enjoy this beautiful branch of physics, and can readily fix for our epoch the luminous physical state of the stars, for transmission to posterity. Not alone the colour of the stars ought in future to be registered in catologues, but also their spectrum. I have already commenced a review of the principal stars, and will Igive a specimen of it as soon as I can.
I will only now mention, as it is very curious, that, among many stars I have examined, y Cassiopea is one which I have found to deserve special attention. This star, of the colour commonly called white (but which should more properly be called green), has a spectrum which is the inverse of the white stars, as of a Lyræ, a Aquilæ, &c. Whilst in these there is a black space in the blue-green, in y Cassiop. there is, in that position, a beautiful bright band. Its spectrum appears that of magnesium, which, whilst burning, gives an uniform spectrum on which the brighter lines are separated. In y Cassiop. the bright lines are different and numerous; but one is dominant, and that takes precisely the place of the black line in those above-named. It is easy to make the comparison by the method above indicated with B Cassiop., which is near it.
Although the principal types of the stellar spectra are restricted (and their uniformity in so prodigious a number of bodies is surprising), on examining them with this spectrometer it is seen that there are marked differences. But y Cassiop. shows that not all the lines are the effect of absorption. In fact, if the dark band of the blue-green in the white stars is the line F of hydrogen, and if it is produced in them by absorption, it must be said that in this star the bright line is produced by direct combustion or by some other particular state of the material.
For objects which have a diameter, this spectrometer is not available; the lines in Jupiter and in Venus are, however, distinguishable, but they are confused : the nebular planets are very well distinguishable from stars, but when they have a diameter the image is not distinct.
I will add that our prism is made by Secretan, and has a dispersive power which is very strong, and is superior to two ordinary prisms, and perhaps to three. Varying the position of the micrometric point from the red to the violet, the star changes in the finder a quarter of a degree, and so the measures can be taken very precisely.
Whoever has not an ordinary spectrometer with a slit, can easily make it with an ocular from an ordinary terrestrial telescope, putting between the two oculars which compose it one of Hoffmann's prisms, and looking with it through a slit, as is done when this ocular is used as a microscope. This method is also available with much facility in the spectrometric study of microscopic objects.
GREENWICH MEAN TIME,
ECLIPSE OF THE SUN. An eclipse of the sun will take place on the afternoon of the 8th October, which will be partly visible at Greenwich.
h. Eclipse begins
Oct. 8, 4
2599 Greatest phase
5 2597 The sun sets at sh. 21m. Magnitude of the eclipse (sun's diameter=1) 0-454; angle from North Pole of first contact 41° towards the West, for direct image.
NOTES AND GLEANINGS.
HERMANN GOLDSCHMIDT.-Since our last issue we have learnt of a loss which will be found a most severe one. Hermann Goldschmidt, the Frenchified-German-portrait-painter-astronomer, was one of a type of men common enough, we are glad to say, in England, but necessarily rare on the Continent-namely, enthusiastic amateurs. Possessed of limited astronomical means, Mr. Goldschmidt stamped his name on the rolls of science by his eminent perseverance ; he discovered no fewer than 13 minor planets, and worked with considerable energy at observations on solar physics. His death occurred at Fontainebleau on August 29. The Illustrated News says that he was the son of a merchant, and was born at Frankfort-on-theMaine, on June 17, 1802. His early years were passed in his father's commercial establishment; but a visit to Holland, when he was thirty years of age, led to his devoting himself to painting, which art he studied with much assiduity at Munich, under Schnorr and Cornelius. In 1836 he proceeded to Paris, which he made his home, and where he produced a number of fine works. About 1847 his attention was accidentally turned to astronomical observation, which he eventually adopted with great ardour; and the fruits of his researches include the discovery of thirteen of the minor planets, the list commencing with Lutetia on Nov. 15, 1852, and ending with Panopea on May 5, 1861. He obtained many prizes and other honours from the Academy of Sciences at Paris and other scientific bodies who recognised the valuable results of his energetic labours, carried on with very humble apparatus on the sixth floor of the Café Procope. Among these should be mentioned the observation of about 3,000 stars not marked in the charts published by the Academy of Berlin, with the concurrence of the most eminent astronomers of Germany.
A New CATALOGUE OF NEBULÆ is being prepared for publication by M. G. Rümker. The first part will comprise objects in the vicinity of the North Pole.
A New MINOR PLANET, No. 89, was discovered by M. Stéphan, at the recently founded Observatory at Marseilles, on August 6.
HANDBOOK OF THE STARS. By Richard A. Proctor. London: Longmans. In this his latest contribution to the science of Astronomy, Mr. Proctor gives us a very useful catalogue of 1500 stars, with their positions to onetenth of a minute of time, for the year 1880. It contains also their magnitude, their numbers from the British Association Catalogue, those applied to them by Flamsteed, and the Greek or other letters by which they aro known. They are arranged in the alphabetical order of the constellations ; and as a handy, useful, working list of stars, at a moderate price, this is the best we have seen. A large portion of the little book is taken up with a description of the method of constructing star maps, comparing the various plans which have been adopted for this purpose ; there are also elaborate tables for the determination of precession, &c., and illustrations, in the shape of maps of portions of the heavens, printed in blue with white stars in a bold and distinct manner.
THE MOVEMENTS OF THE ATMOSPHERE.
(Concluded.) On the evening of " May 22, 1851, at Chickanallenhully, lat. 12° 57', long. 77° 38' E., there was a heavy fall of rain, accompanied after night closed in by thunder, lightning, and hail. The hailstones were for the most part about the size of oranges and limes, which broke the tiles on the roofs of houses, and seriously injured cocoa nuts and betel-nuts, gardens, and many fruit trees, crushing many young trees and breaking down a few larger ones; but neither men nor beasts were injured, all having sought shelter at the commencement of the rain. The next morning many hailstones as large as pumpkins and jack fruit were found on the plain, extending three miles south of the town; and onc immense block, measuring four and a half feet in length, three feet in breadth, and eighteen inches in thickness, was found in a dry well.” *
* In the Himalayas, north of the Peshawur, on May 12, 1853, 84 human beings and 3,000 oxen were killed.
Of the Peshawur storm we have few details beyond the fact that the ice masses were very hard, compact, and spherical, many of them measuring three and a quarter inches in diameter, or nearly a foot in circumference; and this fact seems to have been given from measurement and not by guess.”
Dec. 11, 1854, at Poorundhur, lat. 18° 42' N., long. 14° 12' E. (si .), altitude 3,500 feet
“ Numbers of persons were severely injured by the falling of large ice flakes, many of them weighing several pounds; and the cattle, in considerable numbers, have died from the effects of the storm."
May 11, 1855, at Naine Tal (Nynee Thal), in the lower Himalayas, lat. 29° 30', long. 79 80 (sic.), "A small preliminary shower of rain fell, deep-toned thunder rolled and reverberated, and vivid lightning streamed and blazed over the devoted station. The hail was ushered in by a few bright lens-shaped stones as large as pigeons' eggs; then came more. Many were the weighings and measurings of these monsters over all parts of the station. Some weighed six, others eight, others ten ounces; and one or two more than one and a half pound avordupois, with circumferences ranging from nine to thirteen inches. Though no bullocks were killed, a monkey was, and three human beings were knocked down. Birds were killed, trees barked, and houses unroofed." +
* Buist, Remarkable Hailstorms in India ; B. A. Report. 1855. Transactions of the Sections, p. 35. Original in the Bombay Times.
+ Ibid. p. 37.
The same memoir from which these last four accounts are taken records four occasions in which remarkable masses of ice, several hundred pounds in weight, are believed to have fallen in India. There is no reason to doubt the authenticity of the statements; but it must be assumed that these masses were due to aggregations of hailstones—an hypothesis scarcely detracting from the interest attaching to them.
M. Lacoq, at Clermont, observed on July 28, 1835, a hailstorm, the peculiarity of which was, that the clouds from whence the hail fell undoubtedly possessed a rotatory or whirling kind of movement. *
How accurate is the description given in Holy Scripture, † that " the wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh and whither it goeth." Few meteorological phenomena have been more studied, and yet there is none the theory of which is so little understood. Winds are propagated either by compression or rarefaction, or, as Pouillet terms it, impulsion or aspiration. In the former case they are developed in the same direction in which they blow; in the latter, in a contrary direction. A remarkable instance of an aspiration wind occurred in North America on July 12, 1829. At Albany, a violent gust of wind blew over the town from the SE. when the bells were ringing for church service, but the wind was not felt at New York until an hour later, when the service was half
The direct distance is about miles. It thus originated to the north of Albany, where the pressure of the atmosphere must have been diminished, and extended to the south in a direction contrary to its motion. The celebrated hurricane of Nov. 29, 1836, was propagated by impulsion. It was felt at London at 10h. A.M.; at Amsterdam, at uh. 5m. A.M.; at Hamburg, at 6h. P.M.; and finally reached Stettin at gh. P.M.
Winds may be divided into three classes :-1. Those which are constant, or always blowing in the same direction; 2. Those which are periodical, blowing part of the year in one direction, and part in another and contrary direction; and 3. Those which are variable or erratic. The two former are met with in and near tropical regions; the latter prevail in more temperate climes.
In the British Isles the winds are partly of the periodical and partly of the variable class; for we find that in the spring northerly and easterly winds prevail,“ arising from the currents which flow southwards, to replace the heated air over the Atlantic Ocean,
* Observations cited by De la Rue, in a paper on the Formation of Hail, in Edinburgh New Philosophical Journal, vol. xxi. p. 282, Oct. 1836.
of St. John, iii. 8.