their different aspect to our eyes, may be equally true as applied to their intrinsic splendour. None of these hypotheses, therefore, drive us upon any improbability, while they enlarge our ideas of the wonderful diversity, as well as magnificence, of the works of the Creator. If we now cross the galaxy in an E. direction, till we reach a line down from Polaris through Castor, we find a beautiful first-magnitude star, a Canis Minoris, Procyon, introduced here as a pointer to a delicate pair, too small, otherwise, for our list, but so readily found from its splendid neighbour, and so especially valuable as a test-object, that it well deserves insertion. It lies a little way sƒ from a, in the same field with it under a moderate power, and is the brightest among many companions. It has been often referred to as "31 Canis Minoris (Bode)," having been so designated by that astronomer; but we shall give it Smyth's appellation: 103. 170 P. VII. Canis Minoris. 1" 4. 1329. 7 and 8. White and ash-coloured. Secchi thinks this very pretty double star is in slow angular motion. I have seen the discs in contact with 144 on 37% inches; with 300 on my present 5 inches the division is about equal to one diameter of the smaller star. The remark in Herschel and South's catalogue (1821-1823) that 133, the usual observing power of the 5 feet equatorial, gave no suspicion of its being double, and 303 just separated the discs, would lead to the idea of a widened distance, which, however, the measures of Struve and Secchi do not confirm. We now proceed to two objects which, from want of space, were obliged to be postponed last spring till they had advanced too far into the twilight. The first of them is a glorious double star 104. y Leonis. 2′′-6. 103°2 (1831-36). 28. 107°-2 (1843.18). 2 and 4. Bright orange and greenish yellow. Herschel I. called them white and reddish-white; and as his bias was in favour of ruddy tints, there is a suspicion of change since his day. This has been called the noblest pair above our horizon, for the grandest of all, a Centauri, both of 2nd mag., only begins to be visible in Egypt and conspicuous in the West Indies. It is an excellent test for small instruments. I have divided it well with a beautiful 24 inch glass by Bardou, of Paris, and Smyth found it within the reach of 2 inches. It is impossible to look upon these two golden suns without admiration, and we shall not be surprised to find that they form a binary system. Smyth's measures alone show this; but it is still more evident from Herschel I.'s angle, 83° 20', in 1782, and the recent measures of Secchi, whose mean is 3′′.047 and 108°11 (1858-869). The motion, however, is slow, 220 Occultations.-Dark Transits of the Satellites of Jupiter. and the period must be long; but, perhaps not, as formerly supposed, so much as 1000 years. This object may be found from the great star Regulus (a Leonis, the Lion's Heart), the brightest in a large tract E. of the Twins and Procyon. N. of Regulus, at a short distance, lies a 3rd mag. star, n Leonis; nf from this, at a still less distance, is 7, next after a the brightest in the vicinity. Regulus possesses some interest as marking very nearly the position of the ecliptic, or apparent path of the sun in the heavens, the star being only a few minutes above the N. limb of the sun on August 21 of the present year. Our next is a more difficult object,— 105. Leonis. 24. 90°5 (1836-4). 2′′5. 81°3 (1853·29). 4 and 7. Pale yellow and light blue. This pair, missed by previous observers, and discovered by W. Struve at Dorpat, is no doubt a binary one; its continued retrogradation appears from Secchi, the mean of whose measures gives 2"-568 and 76 38 (1856-263). Its beauty fully entitles it to a trial, but it is too close for a very small telescope. I have seen it well with 3 inches and power 144, 80 only just separating it. It will be caught as the nearest 4th mag. star sp Denebola, a 2nd mag. star in the Lion's tail, which is the most conspicuous to the E. of Regulus, but at a considerable distance, and lying nearly in the direction of Arcturus from the latter star. OCCULTATIONS. The following occultations will be conveniently visible :April 2, B. A. C. 4006 (i. e. the star so numbered in the British Association Catalogue), 6 mag., from 11h. 25m. till 12h. 4m. 26th, Cancri, 5 mag., from 9h. 46m. till 10h. 54m. e Leonis, 5 mag., from 10h. 29m. till 11h. 28m. DARK TRANSITS OF THE SATELLITES OF JUPITER. 29th, Jupiter having now become very conspicuous in the S.E. sky, the dark transits of his satellites will again be objects of curiosity; and as the opposition of the planet takes place on the 12th, the reversion of the relative positions of the satellites and their shadows in the course of the month, and their very close proximity about the time of the opposition, will be noticed with much interest. The following transits are those most convenient for observation:-April 3rd. The shadow of II. leaves the disc at 9h. 52m., followed by the satellite at 10h. 14m. 4th. The shadow of I. enters at 11h. 26m., the satellite following at 11h. 38m. 6th. The shadow of I. passes off at 8h. 8m., the satellite at 8h. 16m.; the shadow of III. at 9h. 28m., III. itself at 9h. 50m.: thus previously to 8h. 8m. two satellites with their respective shadows will be on the disc at the same time. 10th. The shadow of II. is on Jupiter from 9h. 55m. till 12h. 26m.; the satellite from 10h. 3m. till 12h. 28m. 13th. The opposition being past, and the shadows transferred to the other side, I. will be in transit from 7h. 48m. till 10h.; its shadow from 7h. 49m. till 10h. 2m.: at 10h. 54m. and 10h. 59m. the shadow of III. and III. itself respectively enter. 20th. The ingress of I. is at 9h. 32m., of its shadow, at 9h. 43m.; their respective egresses at 11h. 44m. and 11h. 56m. 27th. I. will enter at 11h. 17m., followed by its shadow at 11h. 37m. ANALYSIS OF MIXED FABRICS. THE interesting researches of M. Persoz, jun., on the power of a strong solution of chloride of zinc to dissolve silk, affords the means by which a real analysis of a mixed fabric of silk, cotton, and wool may be made. To dissolve silk, a strong solution of chloride of zinc should be first boiled with excess of oxide of zinc, and the clear solution should be afterwards separated either by decanting or by filtering through a funnel stopped with asbestos. Silk boiled in this solu tion readily dissolves, and if a mixed fabric of silk, cotton, and wool be so treated, the silk only is dissolved out. If the residue of the fabric is then removed, carefully washed so as to get rid of all adhering chloride of zinc, and afterwards boiled in a strong solution of caustic soda or potash, the wool is dissolved, when the remaining cotton, after having been washed from the potash solution, can be recognized under the microscope. The properties of the solution of silk are strikingly shown if the chloride of zinc is got rid of by dialysing. This may be perfectly accomplished if the solution is weak, when a golden yellow varnish of dissolved silk remains in the dialyser; this is viscid and may be drawn out into threads; on evaporation it leaves the silk in a somewhat altered form, the tenacity being much lessened. If, on the other hand, a concentrated solution is dialysed, the whole of the chloride is not got rid of, but towards the conclusion of the operation the silk solution in the dialyser increases very much in size by the absorption of water through the parchment paper, sometimes even to such an extent as to fill up the vessel, and eventually becomes a ropy magma, or tenacious semi-solid mass. This mode of separating the different tissues in mixed fabrics offers an interesting contrast to that adopted by Mr. Ward, in which the wool is destroyed by a heat just sufficient to char it, leaving the cotton or linen in an uninjured state. FLAME-COLOURS. ALTHOUGH a spectroscope is requisite in order to recognize with certainty the various metals in a mixture by means of the systems of coloured rays characteristic of each metal when burning, yet some very instructive and beautiful effects may be obtained with scarcely any apparatus at all. For this purpose it has been suggested* that the chlorates of the different metals should be used. If inside the edge of the flame of a small spirit-lamp, or, better, of a Bunsen gas-burner, a fused bead of chlorate of potash be held in a loop of platinum wire, after a second or two there takes place an explosive flash of violet flame, intense and beautiful; while chlorate of soda gives the well-known yellow light with peculiar brilliancy: but it is, perhaps, with chlorate of baryta that the most striking phenomenon is produced. In this instance it is sufficient to bring a crystal of the salt (which may be readily obtained in commerce) in contact with the flame, when a series of decrepitations occur, accompanied by bursts of the characteristic green light. A pretty effect is seen when chlorate of baryta is introduced into one side of a flame, and chlorate of strontia on the other. The chlorates of lithia, strontia, and lime offer, when thus ignited, a spectacle of great splendour; and if a spectroscope be employed, the blue bands of lithia are clearly seen, although with its other salts the high temperature of the electric arc alone developes them. Chlorate of copper is another compound, the violet-blue flame of which is unusually brilliant when shown as we have described. But it is quite possible to dispense with the Bunsen gas-burner or spirit-lamp, and even with the platinum wire, and yet to obtain results as striking, if not more so. For this purpose some gun-paper, made in the same way as gun-cotton, is to be soaked in solutions of the various chlorates mentioned above, dried with care, and kept dry. A good gun-paper for the purpose is prepared by soaking strips of Swedish filteringpaper for ten minutes in a mixture of four parts of oil of vitriol with five parts of strong nitric acid, both by measure: the strips when taken out of the acid should be washed first with cold, and then with hot rain or distilled water, till the washings Chemical News. A. H. Church, Dec. 24th, 1859, and W. Crookes, April 26th, 1862. are no longer sour to the taste. The solutions of the metallic salts need not be very strong; but if they are warm, the strips of gun-paper will be more easily and completely saturated with them. Since some of the chlorates attract moisture from the air, it is better to dry the papers prepared with these compounds before the fire carefully previous to lighting them. They are shown to best advantage when a strip is loosely crumpled up into a pellet, lighted quickly at one corner, and thrown up into the air against a dark background. They leave, after burning, if properly prepared, no ash whatever. The flame of copper is well seen even with the chloride of that metal, while paper soaked in nitrate of potash shows the flame better than if the chlorate be used. Gun-paper prepared with a very weak solution of chloride or chlorate of thallium shows the characteristic spring-green flame of that metal with great distinctness. Chlorate of baryta, being an article of commerce, may be employed for the preparation of the other chlorates, it being necessary merely to add to this salt in solution an exactly equivalent quantity of the sulphate or carbonate of the metal whose chlorate is desired. For instance, in order to make chlorate of copper, 15.1 grains of chlorate of baryta being dissolved in hot distilled water, a boiling solution containing 12.5 grains of pure crystallized sulphate of copper is to be added to it. Insoluble white sulphate of baryta falls, while the solution, filtered and evaporated, yields the new chlorate in crystals. In some cases, by means of coloured glasses and coloured liquids, interposed between the flame and the eye, it is easy, when two metals are burning together, to shut off the rays due to one metal, and permit those due to the other to reach the observer. If, for example, a mixed potassium and sodium flame be viewed through a piece of deep cobalt-blue glass, or through a flat bottle filled with water rather deeply tinted with aniline purple (mauve), the violet potassium flame is seen, while the far more intense yellow of the sodium spectrum is totally obscured. |
