4C|4 ^ Rev. Mr. Emmett on Gaseous Bodies. [Dec, 



Article VI. 

 On Gaseous Bodies. By the Rev. J. B. Emmett. 

 (To the Editors of the Annals of Philosophy .) 

 GENTLEMEN, 

 In a former paper I committed a considerable error in deduc- 

 ing the law of force in gases from Newtoni Princip. lib. 1, prop. 

 90, which I wish now to correct. Instead of taking that view 

 of the subject, it ought to have been investigated by prop. 90, 

 lib. 2 ; for since the pressure upon the whole surface of a sphere 

 is equal to that of a cylinder of equal density with the atmosphere 

 of the sphere at all equal distances, whose base is equal to the 

 surface of the sphere ; and the force upon an hemisphere is eqtial 

 to that of a similar cylinder whose base is equal to the area of a 

 great circle. Hence the elastic force of a gas will be nearly in 

 proportion to its density. Many curious results relating to the 

 properties of gases follow from the proportion ; but since I have 

 not leisure to make an arrangement ready for the next number 

 of the Annals, I shall content myself at present with giving 

 notice of the discovery of the error ; and shall communicate the 

 proposition, and trace some of its consequences, by the earliest 

 possible opportunity. 



Article VII. 



Telescopical Observations on the Moon, 

 By the Rev. J. B. Emmett. 



(To the Editors of the Annals of Philosophy.) 

 GENTLEMEN, 

 In the figure (see next page) your readers will find an outline 

 of certain appearances of the moon's surface, which I named in 

 my last paper. The figure is not presented as a finished or even 

 accurate drawing ; it merely represents the general appearance 

 of those parts on the N boundary of Palus MceCtis, of Hevelius, 

 Mare Crisium of Cassini, which have the appearance of rivers. 

 I have not measured the parts with the micrometer, because I 

 wish to trace the lines to their full extent ; to obtain a more 

 correct outline of the very numerous similar objects on the 

 S part than I now possess. To free them from illusions, 

 arising from the shadows of ridges and other objects of similar 

 nature, will require observations continued for a considerable 



