Natural History. 201 



found, but there was a considerable portion of soda, and it is 

 accordingly reasonable to suppose that the sulpho-cyanogen had 

 originally been combined with sodium, and only during the evapo- 

 ration become united to the iron. The residuum from the powder 

 which had been successively submitted to the action of ether, alcohol, 

 and water, was now heated with muriatic acid, which formed a 

 transparent solution, and an insoluble gelatinous substance of one- 

 sixth of a grain in weight, after having been dried. The solution 

 was saturated with ammonia, and yielded twelve grains and a quarter 

 of phosphate of lime, with a small quantity of animal substance, as 

 appeared from the smell during combustion. The remainder of the 

 solution being mixed with oxalate of ammonia, formed a precipitate 

 of oxalate of lime, which, on being ignited, was found to be one- 

 eighth of a grain ; besides there were some traces of carbonate of 

 magnesia. Fifteen grains of the salivary concretion would accord- 

 ingly consist of 



0.375 of fatty substance, 



0.250 osmazome, 



i &nn (Sulphates, iron, chloride of calcium, sulpho-cyanide 



J " \ of sodium, 



0.166 Animal substance (mucus?), 



12.250 Phosphate of lime, 



0.212 Carbonate of lime, 



. 247 Carbonate of magnesia, water, and loss. 



15.000* 



III. NATURAL HISTORY. 



1. POWER OF CARBONIC ACID ON THE LUNGS. 



WHEN M. D'Arcet went to visit the very abundant and curious 

 source of carbonic acid, existing at Montpensier, in the department 

 of Puy de Dome, he endeavoured to ascertain personally the effect 

 of the gas when respired. He kneeled down, therefore, near the 

 larger source, supporting himself on his hands, and advanced his 

 head slowly downward, intending to raise himself the moment he 

 felt any indication of risk : but on commencing the respiration of 

 the gas, the effect of feebleness and extinction of power was so 

 sudden, that he fell down flat, with the face entirely immersed in 

 the current of carbonic acid, and would have lost his life, but that 

 the guide whom he had forewarned, raised and carried him away 

 to the fresh air. 



M. D'Arcet proposes two curious uses of the place. The nature 



* Schweigger-Seidel's Jahrb. 1830, iv. 403. 



