M, Berthelot on Formic Acid and Carbonic Oxide. 61 



Assuming tlie depth of the pit to be 1260 feet, and the radius of 



the earth 4000 miles, we have — = f^rynn - Eliminating h from 



equations (1) and (2), and substituting this value of — , we find 



^ = ^41^ (^^ 



To find the value of p, I make use of the following facts : — 

 According to Humboldt, the mean height of the continents above 

 the sea-level is 1000 feet ; and according to Rigaud, the relative 

 areas of land and water are as 1 to 2*815. Hence, since the 

 bottom of the coal-pit is 1200 feet below the sea-level, if we 

 suppose all the land and water blended into one couche of a 

 thickness of 1200 feet, and denote its mean density by p, we 

 find, assuming the mean density of the land to be 2*75, 



2200 X I X 2-75 + 1200 x w; x 1 = 1200(z^ + /)/); 



w denoting the area of water, and / the area of land ; and sub^ 

 stituting for these their values, we obtain finally 



p = 2-059 (4) 



Substituting this mean density of the land and water at the 

 surface for p in equation (3), we find 



A =5-480. ....... (5) 



This result agrees closely with the best experiments made with 

 the torsion balance, and appears to be fairly deducible from th^ 

 observed facts, considered in a general point of view. 



Trinity College, Dublin, 

 June 18, 1856. 



VII. Chemical Notices from Foreign Journals, 

 By E. Atkinson, Ph.D. 



[Continued from vol. xi. p. 461.] 



IN the April Number of the Annates de Chimie et de Physique, 

 Berthelot has an important paper on the relation between 

 Formic Acid and Carbonic Oxide. 



Carbonic oxide bears the same relation to formic acid that 

 olefiant gas does to alcohol : — 



C^O^ + 2H0 = Q^WO\ 



Carbonic oxide. Formic acid. 



. C^H^ + 2H0 :^ C^H^O^; 



defiant gas. Alcohol, 



and formic acid, heated with strong sulphuric acid, gives carbonic 

 oxide; just as alcohol, by the same treatment, gives olefiant gas. 



E2 



