1835.] by M. F. Le Play. 27 



year, which raised the price of the metal. The Galena, 

 from the Sierra de Gador, is used in the state in which it 

 comes from the mines, in thirty-one different works, com- 

 prising sixty-nine reverberatory furnaces, and fifty-eight 

 common furnaces ; the minerals affording, by the former 

 method, sixty-six per cent. The mountainous nature of 

 the country renders the formation of good roads imprac- 

 ticable, and hence, the product of the mines is carried, by 

 numerous troops of asses and mules, first to the works, 

 and then, after reduction, to the ports of Adra, Roquetas, 

 and Almeria. 



Article III. 



On Respiration. By Thomas Thomson, M. D., F. R. S., 

 L . and E . , &c . Regius Professor of Chemistry in-the Uni- 

 versity of Glasgow. 



When the experiments on respiration were made by 

 Lavoisier, Goodwin, Menzies, Davy, &c, towards the end 

 of the last century, it seems to have been the generally 

 received opinion, that every individual by inspiring the 

 air into his lungs, produces the very same change upon it. 

 At least, the conclusions respecting respiration to be met 

 with in Physiological and Chemical books, depend for their 

 accuracy, upon this assumption. Nothing, however, can 

 be farther from the truth. The chemical changes produced 

 in air by respiration, vary in their extent, not only in 

 different individuals, but even in the same individual at 

 different times ; and that to such an extent, that if we 

 analyze air thrown out of the lungs at different times, we 

 find the quantity of carbonic acid, sometimes not to exceed 

 two per cent, and at other times to amount to more than 

 seven per cent. Dr. A. Fyfe and Dr. Prout have shown 

 many years ago, that an alteration is produced in the 

 quantity of carbonic acid in the air expired, by the mode 

 of living of the individual : that when the constitution is 

 affected by mercury, the proportion of that gas in the air 

 expired is diminished, and that it is diminished also by 

 nitric acid, by spirits, and by a vegetable diet. But I have 



