'Natural History Society, 229 



cessary by lie theory of types in chemistry and by the dynamical 

 theory of heat. 



Deville and Debray recommend for the economical production 

 of oxygen the calcination of sulphate of zinc, which at a heat less 

 than that required to decompose biiioxide of manganese breaks 

 up into a light white oxide suitable for painting, sulphurous acid, 

 and oxygen. As another and even preferable process they re- 

 commend the decomposition of sulphuric acid, by allowing a thin 

 stream to traverse a vessel containing platinum sponge and heated 

 to low redness. Oxygen and sulphurous acid are the results. 

 The methods of removino; the latter are obvious. 



M. Carr^ freezes water by the cold produced by evaporation of 

 liquid ammonia. His apparatus consists of two iron cylinders, 

 the one three times the magnitude of the other, connected air 

 tight by a tube. »The larger vessel filled with a strong solution 

 of ammonia is heated to about 140°. The smaller vessel is at 

 the same time immersed in cold water. The ammonia expelled 

 by heat from the larger liquefies in the smaller cylinder. On re- 

 moving and cooling the larger vessel the ammonia is reabsorbed 

 by the water so rapidly as to reduce the temperature of the other 

 portion of the apparatus to the freezing point of mercury. 



Kopp suras up the results of his investigations respecting the 

 relation between composition and boiling point. They are briefly 

 these. An alcohol On Hn^o ^2 boils at a temperature of 

 (40-|-9.5n) ^Cent., the corresponding acid Cn Hn O4, at 40° 

 higher, and the isomeric compound ether at 82° higher still. 

 The related alcohols, acids and ethers Cn Hm O,^, Cn Hm 0^ 

 and Cn Hm O4 boil at temperatures easily calculated by adding 

 or subtracting 5° for every H in this formula more or less than 

 is in the similar formula of the above series, to or fiom the boil- 

 ing point of its related compound. After pointing out similar 

 relations in less extensive classes of substances, he calls attention 

 to the importance of the boiling point of a substance in aiding us 

 to determine its affinities. s. p. r. 



NATURAL HISTORY SOCIETY. 



The Natural History Society of Montreal, met on the evening 

 of the 29th April, in their Rooms. 



The Lord Bishop of Montreal presiding. 



The following donations were presented and ordered to be 

 acknowledged : — 



