190 [June 19, 



As soon as a quantity of the latter can be prepared, I hope to iso- 

 late the acid. 



Salts of the oxides of barium, magnesium, strontium, silver, zinc, 

 manganese, and chromium have been prepared by the direct action of 

 bisulphide of carbon. Some of these differ considerably from the 

 salts prepared by Berzelius by the action of the bisulphide of carbon 

 upon the sulphides of the metals. The process which furnishes the 

 lime-salt well crystallized will be tried with other compounds, and the 

 results submitted to the Society. 



A very offensive suffocating gas is evolved during the decomposi- 

 tion of bisulphide of carbon by lime, which is injurious, if not poi- 

 sonous ; and having suffered severely from breathing this and other 

 noxious compounds derived from the same source, I think it right to 

 call attention to it. I hare formed a gas of similar properties by 

 passing bisulphide of carbon and hydrogen together through heated 

 lime, and should not be surprised if it prove to be the long- sought 

 simple sulphide of carbon. 



Slightly ammoniacal alcohol breathed from a cloth appears to be 

 the best restorative for the severe depression caused by respiring the 

 offensive gases and vapours above named. 



XX. " On the Geometrical Isomorphism of Crystals." By the 

 Rev. W. MITCHELL. Communicated by Dr. FBANKLAND. 

 Received June 12, 1862. 



In a paper " On the Geometrical Isomorphism of Crystals," pub- 

 lished in the Philosophical Transactions for 1857, by H. J. Brooke, 

 F.R.S., it was shown that all the substances crystallizing in the 

 various forms of the pyramidal and rhombohedral systems might 

 be regarded to be as isomorphous as those belonging to the cubical 

 system. 



This isomorphism was shown by so taking the arbitrary primitive 

 pyramid of the one system, or the rhomboid of the other, as to bring 

 these forms nearly isomorphous for every substance in the one system 

 or the other. In this way tables were formed showing that the same 

 notation for any form would be not strictly isomorphous, but plesio- 

 morphous for any other form of another substance bearing the same 

 notation. 



