1822.] Proceedings of Philosophical Societies. 153 
constant angle of any prism be divided by the power of the 
telescope to which it is applied as a double image‘micrometer at 
the eye end, the quotient will be the measure of the angle, sub- 
tended by a line joining the centres of the two images of the 
objects observed. Therefore if the natural constant angle of any 
prism be divided by the measure obtained with any given power, 
the quotient will be that power, the constant angle being a quan- 
tity always equal to the product of any power by its correspond- 
ing measure.” 
(To be continued.) 
ARTICLE X. 
Proceedings of Philosophical Socieiies. 
ROYAL SOCIETY. 
On the ultimate Analysis of Animal and Vegetable Sub- 
stances, by Andrew Ure, MD. FRS. 
= the Analysis of Sea Water, by Alexander Marcet, MD. 
In this paper, the whole of which was not read, Dr. Marcet 
shows that the waters of the ocean do not contain mercury, as 
has been supposed, and that muriate of ammonia is a constant 
ingredient. 
ArTIcLe XI. 
SCIENTIFIC INTELLIGENCE, AND NOTICES OF SUBJECTS 
CONNECTED WITH SCIENCE. 
I. Hydriodide of Carbon. 
In the Philosophical Transactions for 1821, Mr. Faraday described 
a compound of iodine and olefiant gas, but he had not at that time 
the means of ascertaining its composition. Since that period he has 
obtained it in greater quantity, and analyzed it. Four grains were 
passed in vapour over heated copper in a green glass tube ; iodide of 
copper was formed, and pure olefiant gas evolved, which amounted to 
1-37 cubic inch. As 100 c. i. of olefiant gas weigh about 30°15 grs. 
1°37 c. i. will weigh 0413 gr. Now 4 grs. — 0-413 leave 3°587 
iodine, and 3°587 : 0°413 :: 117°75 : 13°55 nearly. Now 13°55 is so 
nearly the number of 2 atoms of olefiant gas that, according to Mr. 
Faraday, the substance may be considered as composed of 
1 atom of iodine...........- BES viecmpusie 11775 
2 atoms of olefiant gas. ..... eweee dence 13°4 
