greater, proving that the light of the galaxy is indeed due entirely to the multitude of distant stars. To give some idea of the scale of this multiplication, it may be mentioned that on one occasion Sir William Herschel estimated that not less than 116,000 stars must have passed through the field of his telescope in a single quarter of an hour. The course of the Milky Way amongst the constellations is principally, so far as visible to us, through Auriga, Cassiopeia, Cygnus, Aquila, and Sagittarius. In the latter, which is always low in the sky in these latitudes, is a part especially rich in stars. In Auriga the brightness is much less than elsewhere. In Cygnus there is a confused and irregular part, from which three partial streams diverge.

The Pleiades in Taurus are known to all. Viewed with the naked eye, most persons can only see six stars, but those possessed of acute sight see seven, and there is at least one authentic instance of as many as twelve having been so seen (by a lady). With a telescope, a group of fifty or sixty stars becomes visible, crowded together in a very moderate space. In the constellation Cancer, near the star e, and between y and 8, is a curious luminous spot called Prosepe, or the Beehive, which a very ordinary telescope shows to consist of a multitude of stars. Another telescopic cluster is situated in the sword-handle of Perseus, which may be considered as an offshoot of the Milky Way. It is nearly in a line between y Persei and & Cassiopeia.

Of the nebulæ it is scarcely desirable to speak here. Several of them are only immense clusters of stars, so distant as to require very powerful telescopes to resolve them, whilst others (especially the spiral nebulæ discovered by Lord Rosse) appear to possess a peculiar constitution of their own. The most remarkable one is the great nebula of Orion, over which many stars are scattered, but of which every increase in instrumental power shows fresh features. The sword of Orion consists of three stars, visible to the naked eye, called c, 0, and ; the

middle one, 'Orionis, marks the principal part of the nebula, which is, indeed, perceptible to the unaided sight. A moderately good telescope shows four stars of unequal, but not greatly differing, magnitudes, in the form of a trapezium. The subject of double and multiple stars is, indeed, a most interesting part of astronomical research, many having been proved to have motions about each other of different periods. But the greatest part of the binary or physically double (as distinguished from merely optically double) stars are too close to be seen separate, except when high magnifying powers are applied to them. A few of the stars which may be seen double with comparatively small telescopes may be named here. They are, beginning with the closest pairs, Castor (magnitudes of components 3 and 3), y Arietis (4 and 5), Ursa Majoris (0 and 5), 61 Cygni (5 and 6), and 3 Serpentis (4 and 5).

It is obviously important for any one interested in astronomical observing to make himself familiar with the names of the constellations, and of the principal stars in each, so as to know them at sight. Mr. Proctor's Star Maps, adapted to the different constellation seasons of the year, are admirably suited for this purpose.

Good service may be done by amateurs who possess a knowledge of the stars in observing and recording the paths of remarkable meteors which they may happen to see. This has now become a branch of astronomy, and one of high interest. No telescope at all is required for its prosecution; but we are unwilling to close this article without reminding persons able to take part in these observations of the necessity of an accurate acquaintance with the stars, without which it is impossible to record the place of a meteor in such a manner that any use can be made of it. The times of appearance and disappearance, as well as the places where these are seen amongst the stars, should be noted if possible. The periods at which shooting-stars are most frequently seen are about April 20

21, August 7-13 (especially 9-10), October 16-23, November 12-14, and December 6-14.

For very valuable collections of astronomical data of every kind, we would refer the reader to Mr. Chambers's 'Descriptive Astronomy,' published by the Clarendon Press in 1867.

We must append to this brief survey of objects for astronomical observation a few words concerning telescopes, the instruments which have so immensely increased man's knowledge of the great globes around him. They are, as is well known, of two kinds, the refracting and the reflecting telescope. In the former, the rays of light proceeding from any point in a celestial object are brought to a focus by refraction through the object-glass, which consists of two closely-fitted lenses of two kinds of glass so combined as to destroy, or nearly so, the colour produced by chromatic dispersion (whence such a telescope is called an achromatic). In the latter, the rays are brought to a focus after being reflected on a properly-shaped metallic surface, called a speculum. In both the image of the object, thus formed by the convergence to a focus of the rays proceeding from any point in it, is magnified by a kind of microscope, called an eyepiece. Now as the latter magnifies the image without increasing its brightness, or the amount of light by which it is produced, it is evident that if an eye-piece of too large a magnifying power is applied to any image, its light will become too faint to permit it to be well observed. If, therefore, it be desired to obtain good observations under a high power, it is necessary to employ a large object glass or speculum, which will collect so large a quantity of the rays diverging from the object observed as to produce an image of considerable brightness, admitting of a good degree of magnification by the eye-piece without having that brightness too much diminished. As a larger amount of light is lost by reflection than by refraction, the image formed by an object-glass will bear the application of a higher magnifying power than

one formed by a speculum of the same diameter.

The steadiness of the image is of as much importance as its brightness. However steadily the instrument be mounted and adjusted (to both of which great attention should, of course, be paid), atmospheric disturbances will always produce a certain amount of tremor, which is increased in proportion to the magnifying power under which the object is viewed. As the degree of this disturbance depends upon the state of the atmosphere at the time, the same amount of power cannot always be employed with advantage upon the same instrument. Good telescopes, therefore, are provided with several eye-pieces, which can be used according to the particular condition of the atmosphere at the time of observation. Actual trial is the only certain test of this. The possessor of a telescope too small to admit of much change of power had better give up trying to use it when he finds the night is not favourable in this respect. The best object to try it upon is a moderate-sized star, the image of which, when brought well into focus, should be very small and round, free from rays or false images, excepting one or two narrow rings of light, circular and concentric with the image surrounding it. Jupiter and Saturn, and particular regions in the moon, are also good test-objects. It was remarked by one of our most experienced observers (but recently called away) that an east wind was not favourable for astronomical observing, as there was always on such occasions a tendency to triangularity of form in the spurious disc which a fixed star appears to have in a telescope. Objects such as comets, which possess a very feeble amount of light, cannot be seen with eye-pieces of high power, as they diminish that light too much; but to see them well requires an object-glass of large aperture, and an eye-glass which does not magnify much. We cannot too strongly impress upon the amateur to be particular in putting his eye-piece in good focus for his own eye at the actual time of observing. In a good instrument a slight dis

placement in this respect makes a considerable difference, and the disc becomes, when viewed out of focus, a large luminous round patch. The disc of a fixed star being spurious (depending for its size upon the aperture of the object-glass), can never be well defined at its edges, but the planets, showing in a telescope real discs, ought, especially Jupiter and Saturn, to have a welldefined outline.

It can hardly be necessary to recommend the owner of a telescope to be extremely careful in its preservation, to keep every part clean, and to avoid exposing it to blows or strains. When it is necessary to

wipe the object-glass, it should be done with great delicacy, using silk, or some other soft material.

In conclusion, we would remark that, although as science progresses, its battle-field becomes more and more appropriated by those who have large instruments at their command, the more easily-seen phenomena being more and more exhausted, yet from time to time instances occur which prove that even now it is possible to add something to our knowledge by the diligent use of means which might have been thought utterly inadequate to produce any such result. W. T. LYNN.