1876.] Presents. 459 



where TTL is a constant. It must be carefully observed that v and v in 

 equation (A) are the volumes of the gas on different isothermals. 



It follows from these results that, in the case of a body in the ordinary 

 gaseous state, if the relations of pressure and volume are known at any 

 one temperature, the corresponding relations at any other temperature 

 can be calculated from the observation of a single homologue at the second 

 temperature. Thus the whole relations of volume and pressure will be 

 known from a set of primary observations at a fixed temperature and 

 the determination of one homologue for each of the other temperatures. 



The general form of the primary curve itself, or curve exhibiting the 

 relations of pressure and volume at a given temperature, is next investi- 

 gated ; and the author finds, as the result of all his experiments under 

 very varied conditions of temperature and pressure, that the value of 

 e(l— p) is constant for the same temperature. Hence we have for the 

 third equation of the ordinary gaseous state 



v(l-pv) = c (C) 



From this last equation the relations of homologous points, as defined 

 by equations (A) and (B), may be deduced. 



The author concludes with some general observations on the action of 

 the internal attractive forces in the ordinary gaseous state, and also on 

 the resistance to diminution of volume which, under certain conditions, 

 modifies largely the effects both of external pressure and of internal 

 attraction. 



Presents received, April 6, 1876. 

 Transactions. 



Angers : — Societe Industrielle et Agricole. Bulletin. 4G e annee. l er 



trimestre. 8vo. 1875. The Society. 



Cherbourg : — Societe Rationale Academique. Mcmoires. 8vo. 1875. 



The Society. 



Lund:— Universitet. Ars-skriffc (Acta). Tome XI. 1874. Mathe- 



matik och Naturvetenskap. 4to. 1874-75. Biblioteks Accessions 



Katalog, 1872, '73, 74. 8vo. 1873-75. The University. 



Montreal: — Natural-History Society. The Canadian Naturalist and 



Quarterly Journal of Science. New Series. Vol. VII. No. 7, 8 ; 



Vol. VIII. No. 1. 8vo. 1875. The Society. 



Perpignan : — Societe Agricole, Scientifique et Litteraire des Pyrenees 



Orientales [Memoires]. Vol. XVIII., XXI. 8vo. 1871-74. 



The Society. 

 Eome: — Accademia Pontificia de' Nuovi Lincei. AttL Anno 28. 

 Sess. 7 ; Anno 29. Sess. 1, 2, 4to. Roma 1875-76. 



The Academy. 



