268 Dr. Hall on the Agency of Carbonic Acid. 



detailed, that this part of the definition is strictly true in regard 

 to iron, one of the five metals included in that subdivision. I 

 consider this point of some importance ; for the classification 

 of M. Thenard appears to me singularly useful in the study of 

 the properties of the metals. 



It may be observed, from the experiment first detailed in 

 this paper, that it is impossible totally to deprive water of its 

 uncombined gases by the longest boiling. I was never able to 

 preserve iron and water together, without the eventual decom- 

 position of the latter, until I adopted the plan of withdrawing 

 the carbonic acid by means of lime water or magnesia. 



I would now observe, that it is not impossible that the prin- 

 ciples elucidated in this paper may be useful in the arts, and 

 especially that they may suggest the proper means of preserving 

 polished iron goods free from tarnish or rust in damp weather 

 or situations. This object would be effectually attained by 

 covering their surface with lime mixed with water. 



I would state, in conclusion, that the experiments which 

 have been detailed were all made at the ordinary temperatures 

 of the atmosphere, and at every season of the year. Some of 

 them remained for repeated observation during a year and 

 half, for I was anxious that there should remain no source of 

 fallacy in regard to their results. 



Comments on Corpulency. — jBi/ William Wadd, Esq., F. L.S. 



(Continued from page 29.) 



We have now to illustrate the preliminary remarks ; this will 

 be best efiected by extracts from the communications of 

 correspondents. The first extract is from a very sensible, 

 well-informed, studious friend. He gives a succinct account of 

 his feelings, which present an outline, or sketch, of which 

 eveiy practitioner in the metropolis could produce a duplicate, 

 and of which every respectable medical man could furnish 

 a more highly-finished portrait than this, and those which fol- 

 low it. Be it so ; I shall present my collection, as I would 

 portraits of another description, feeling, that those who could 

 give a better delineation and colouring of the facts of my 



