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Observations and Measurements of the Planet Vesta. By John Jerome 

 Schroeter, F.R.S. Read May 28,1807. [Phil.Trans. 1807,^.245.] 



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 1st of April to the 1 1th of May; from which it appears that 

 this planet, now called Vesta, became stationary between the 8th 

 and llth 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 eye. 



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 -rVirirths 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 sam,e region between Mars and Jupiter, in which the three 

 other lately discovered planets perform their revolutions round the 



A new Eudiometer, accompanied with, Experiments, elucidating its Ap- 

 plication. By William Hasledine Pepys, Esq. Communicated by 

 Charles Hatchett, Esq. F.R.S. Read June 4, 1807. [PAz7. Trans. 

 1807, p. 247.] 



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 kndwn, Mr. Pepys 

 traces cursorily the progress of eudiometry from Hales, who first ob- 

 served 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 substituted 

 for 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. 



