Page:Proceedings of the Royal Society of London Vol 1.djvu/290

Rh

The observations contained in Mr. Schroeter’s communication, comprise thOSe of Dr. Olbers, made at Bremen, from the 29th of March to the 6th of May, and those of Mr. Bessel at Lilienthal, from the lst of April to the 11th of May; from which it appears that this planet, now called Vesta, became stationary between the 8th and 11th of May, and is now progressive.

Mr. Schroeter endeavoured also to ascertain her magnitude; with magnifying powers of 150 and 300 applied to a 15-feet reﬂector she seemed equal to a star of the 6th magnitude, but without any ap- pearance of a disc. Mr. Schroeter, and his assistant, both saw the planet at that time with the naked eyc.

As they had formerly observed Ceres, Pallas, and Juno, with a 13-feet reﬂector, and with eye-glasses magnifying 136 and 288 times, they now examined Vesta with the same telescope and the same powers, and found her appearance to be exactly the same, her appa- rent diameter not exceeding 1%ths of a second, which Mr. Schroeter says is only one half the apparent diameter of the 4th satellite of Saturn. Mr. Schroeter considers the intensity and unsteadiness of its light, together with its extraordinary smallness, as very remark- able for a. body which, according to the calculations of Dr. Gauss, is in the same region between Mars and Jupiter, in which the three other lately discovered planets perform their revolutions round the sun. .

After some preliminary observations upon the important part that atmospheric air performs in numerous processes of nature and art, and upon the variety of other gaseous bodies now knbwn, Mr. Pepys traces cursorily the progress of eudiometry from Hales, who ﬁrst observed a contraction upon the admixture of atmospheric air with an air that he had obtained from spirit of nitre and pyrites. The cause of this contraction, and the nature of the nitrous gas that occasioned it, were more distinctly discovered by Dr. Priestley, who also pointed out the use to which it might be applied for ascertaining the purity of air; and he employed for that purpose a graduated tube, which he denominated an eudiometer.

Phosphorus, and the liquid sulphurets, were afterwards substitutedfor nitrous gas; but these being found tardy in their operation, or if accelerated by heat fallacious in their results, Mr. Davy proposed the solutions of sulphate, or muriate of iron impregnated with nitrous gas, as sufﬁciently sudden in their action, and more uniformly free from contamination by other gases.