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croaches 0"-2 or 0-3 on the ring A. By carrying my eye across from the black division on one side to the other, I can see that, if continued in an uninterrupted line, it would cut off a thin slice from the edge of the ball. With very high powers (705 to 1000) the difference of color of the southern edge of the ball, and the ring A at that point is more marked than with the lower powers; and long scrutiny with them confirms my impression that the ball encroaches slightly on A."

“101 36m±G. M. T. Applied an excellent Huygenian eyepiece, giving power 860. It is admirable. The difference of color of the southern edge of the ball and ring A is obvious; and there is no doubt at all of the slight encroachment of the ball on its interior edge. Finding the light of the planet produce a very unfavorable effect upon my eye while endeavoring to estimate the degree of encroachment of the ball on A, it occurred to me to apply my solar eye-piece for the purpose of excluding the rest of the ball and rings, and leaving visible only the southern portion of the ball and the adjacent portion of the rings A and B. Power 506 (the highest, a double-convex lens). The effect is admirable. My eye having rested upon it for some time, the outline of the southern edge of the ball was far more distinctly seen than before, and leaves no doubt of its encroaching on the interior edge of A, to about 03 by careful estimation. At times a little mottling can be discerned very near the southern limb of the ball. Its color is very different from that of ring A; and it completely interrupts the black division which comes sharply up to the ball on both sides of it."

5. The Shadow of the Ball on Ring B. On this appearance I have noted as follows:

"1854, Sept. 26.

a straight line."

The shadow of the ball on ring B is nearly

On Sept. 29 the projecting portion of the shadow, which has been noticed the last two or three years, was seen for the first time this season on the eastern side of the ball;

Ball

1.

B

cutting off the acute point of the ring B intercepted between the edge of the ball and the black division, as at a in the sketch, in which the appearance is much exaggerated.

At the saine date I have remarked,-"I doubt if the shadow

of the ball on ring B is really a straight line, though nearly so. It seems to be a little curved towards the southern end of it, close to the division." In the place indicated the edge is conver towards the ball.

B

SECOND SERIES, Vol. XXI. No. 62.-March, 1856.

2.

21

Ball

"Nov. 26. Only a very narrow line of shadow from the ball falls on the west side, but there is a curious angular projection in the shadow on both the west and east sides of the apex of the ball."

"Dec. 7. The annexed sketch shows the form of the shadow

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4.

6. The Satellites. I have usually estimated Tethys to be brighter than Dione, even when it has been nearer to the planet. This was remarkably the case on the 10th of this mouth, at 7h±G. M. T., when both the satellites were near their greatest western elongation. At 11h 19m G. M. T., Dione, Tethys, and Enceladus, formed an equilateral triangle south-preceding the western end of the ring, thus,

In No. 929 of the Astron. Nachrichten, is a most interesting account by Professor Secchi of the appearance of Saturn in the Munich equatorial refractor, recently erected at the Observatory at Rome. The dimensions of the telescope are the same as those of the Dorpat refractor, the aperture of the object-glass being 9 Paris inches. The Professor characterizes the night of Nov. 19 as one of extraordinary excellence, and doing full justice to the telescope. He describes the dark line on ring A as being just like a pencil line drawn upon it, which perfectly agrees with the views I have had of it since 1851; and with my description as "narrow, very dark, but not black." And when the dusky hue of the ring A is considered, it seems probable that this line would appear almost black if contrasted with a much brighter ground, such, for instance, as the exterior edge of the ring B. It deserves to be remarked that a dark line, precisely similar to this in appearance and situation, was seen on the northern surface of this ring, in the year 1838, by Professor Encke; and by Mr. Lassell and myself in 1842 (when we were not aware of Encke's observation). It may not be a division in the ring, as it was then supposed to be; but, if it is not, it is certainly extraordinary that precisely the same appearance should exist on both surfaces of the ring, and should be, as it would seem, a permanent phenomenon in respect of its situation on the ring, and the darkness of its shade.

Professor Secchi has also described the step-like concentric bands of shading on ring B, exactly as they were described by myself on October 26, 1851: and as I have occasionally seen them almost precisely in the same way to the present time, it may fairly be concluded that they form a permanent feature of this ring. The Professor does not notice the comparatively bright line at the interior edge of B, which seems to me to ren⚫ der that edge pretty definite, though it is certainly less bright now than it was two or three years ago.

In one important point the impression received by Professor Secchi differs decidedly from my own, as stated in the present paper: viz., the place to which the southern edge of the ball is seen to extend on the rings. He states that the opening of the ring is such, that the upper edge of the ball exactly touches the inte rior edge of the black division between A and B, which was visible throughout the whole of its elliptic perimeter. It is singular that, on the 26th of September I arrived at precisely the same conclusion; but the state of the air was not such as to permit the advantageous use of high powers; and my subsequent observations, under much better circumstances, and especially on the 10th of this month, convinced me that my first impression was erroneous, or that a change to a considerable, and in fact unaccountable, amount had taken place.

The first satellite of Saturn (now usually called Mimas) is stated by Professor Secchi to have been seen on November 19th, near its great western elongation; having been found by putting the planet nearly out of the field, and afterwards seen steadily with the planet in full view. It is surprising that he does not mention Enceladus, which must have been close to Mimas at that time, if the latter occupied the place indicated. As my telescope has not shown me Mimus, I cannot say where that satellite might have been; but my own observations prove that Enceladus occupied precisely the situation which the Professor has ascribed to Mimas; and I cannot but think it probable that further observations may have convinced him that it was not the first, but the second, satellite which he saw.

The bright zone on the ball, which commences almost precisely at the equator, and extends northwards as far as the ring permits it to be seen, forms one of the most conspicnous features of the planet. It has been repeatedly referred to by Professor Secchi, as caused by the reflection of the sun's light from the surface of the ring. Two considerations seem to me to be quite conclusive against its arising at all from that canse. One is, that this bright zone occupied precisely the same situation, and was very conspicuous, when the plane of the ring passed through the sun. (See "Remarks on the Planet Saturn," by the Astronomer Royal, in the Greenwich Observations for 1844, p. 44.)

The other is, that the reflection of the sun's light from the southern surface of the ring, which now receives it, must necessarily fall upon the southern hemisphere of the ball, which has been remarkably dark ever since the southern surface of the ring has been illuminated; while the bright zone lies wholly in the northern hemisphere. The remarkable obscurity of the southern hemisphere at the present time seems to indicate that the effect of the reflection from the surface of the ring is quite inappreciable as seen from the earth.

Wateringbury, Jan. 11, 1855.

Postscript." Jan. 14. The night proving fine, I again carefully examined Saturn, and made the following entry in my journal:

12h 45m G. M. T. Saturn is very fine at times, though about 33 past the meridian. It bears 705 very well; and with this power I have no doubt of the southern edge of the ball extending over the division between A and B, and encroaching a trifle on the interior edge of A. With low powers (355 or less) there is sometimes an appearance of the division extending across; but I am persuaded that this arises from the combined effect of the division coming up on each side so near the apex, and the very deep tint of the apex itself, which I think is darker than the darkest part of the broad belt close to the equator of the planet. It is certainly much darker than the ring A.'"

ART. XX.-On a new and advantageous mode of preparing Aluminium; by Prof. H. ROSE.

[Translated and read before the National Institute, Washington, D. C., Oct. 5, 1855, by J. TYssowski, U. J. Dr.*

SINCE the discovery of Aluminium by Wöhler, Déville has recently taught us a method of obtaining it in larger connected masses, in which this metal shows qualities, which had not been observed in the metal as obtained in the form of a powder by the process of Wöhler. While in the latter form it burns with great brightness to a white clay, it may be, if fused into larger balls, heated to redness, without perceptibly oxydizing. These differences may be attributed to finer division and greater density, although according to Déville, Wöhler's metal contains some platinum which accounts for its less fusibility.

After the publication of Déville's investigations I tried also to obtain aluminium from chlorid of aluminium and sodium, by means of an additional dose of sodium. I did not follow entirely the method of Déville, but stratified the salt with the

Poggendorff's Annalen, vol. xcvi, page 152.

sodium and then applied heat. I however obtained no satisfactory results. Rammelsberg also followed closely the method of Déville but obtained no good results; moreover he was seldom able to prevent the bursting of the glass-tubes with which he experimented in consequence of the action of the vapors of sodium upon the chlorid of aluminium. It appeared to me that considerable time, labor, expense and long experience would be necessary in order to obtain even small quantities of this remarkable metal.

The application of chlorid of aluminium and its compounds with the alkaline chlorids, is particularly objectionable for the reason that they are volatile, attract moisture very readily, and therefore the access of air must be prevented when treating them with sodium.

I therefore early thought of substituting for the chlorid of aluminium the finorid of aluminium, or rather the compounds of the latter with alkaline fluorids and which are known to us from the investigations of Berzelius. Berzelius pointed out the strong affinity of fluorid of aluminium for fluorid of potassium and fluorid of sodium, and that the cryolite occurring in nature is a pure combination of the fluorid of aluminium with the fluorid of sodium.

This compound, in consequence of its constituents, is as well. adapted to the preparation of aluminium by means of sodium, as the chlorid of aluminium and its compound with chlorid of sodium. And in addition to this, the cryolite not being volatile, easily reducible to the finest powder, free from water, and not attracting moisture from the atmosphere, it presents peculiar advantages in comparison with the fore-mentioned compounds.

I succeeded in fact in obtaining aluminium by heating powdered cryolite with sodium to redness in a small iron crucible much more easily than by a similar treatment of chlorid of aluminium and its compound with chlorid of sodium. The scarcity of the mineral however prevented me from continuing my experiments.

A short time since, I returned to them, on having obtained through Mr. Krantz in Bonn, a considerable quantity of the purest crystals and at a trifling expense (1 kilogram for 2 Prussian dollars). But my zeal was exalted by the unexpected news reaching me that cryolite may be obtained here in Berlin and at incredibly low prices.

Mr. Krantz had communicated to me his having heard that cryolite exists in masses in commerce, yet he could not learn where. A short time since Mr. Rüdel the Superintendent of the chemical manufactory of Mr. Kunheim near the Halle gate, presented to me a specimen of a white coarse powder, large quantities of which it is said have been sent from Greenland, through Copenhagen to Stettin under the name of mineral soda

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