34S Analysis of Scientific Books. 



of more than 20 gases, with a decree of care and accuracy 8el« 



dom equalled, and never surpassed*." 



Dr. Apjolin in his " remarks on the influence of moisture in 

 modifying the specific gravity of the gases," inserted in the 

 number of the Annals, for May, 1822, justly says of Dr. Thom- 

 son, " his mode of estimating the effect of moisture on the 

 densities of the gases, appears to me altogether incorrect. The 

 principle of the method adopted by Dr. Ore for the same pur- 

 pose is true, but his number for steam being too high, his re- 

 sults are erroneous." Dr. Ure's number for the specific gravity 

 of the vapour of water at 212°, is 0.625, and 0.624 is the num- 

 ber given by M. Biot, in his Traite de Physique, on the autho- 

 rity of M. Gay-Lussact. Nothing is there said of temperature, 

 though it appears that M. Gay-Lussac in his valuable researches, 

 did give the relative densities of steam and air, for the boiling 

 point of water at \^, or 0.625. This is also the theoretical 

 quantity, regarding two volumes of vapour of water, as consist- 

 ing of two volumes of hydrogen .... 0.13838 

 1 of oxygen .... 1.11111 



1 .24999 

 onehalf of which sum = 0.62.5, is the specific gravity, air at 212® 

 being 1.000. But as 1.375 parts of air at 212° become 1,058.33 

 at 60°, we shall have the density of steam at 212° to that of air 

 at 60°= 0.625 x if.H^^ — o.481 and not 0.472, as adopted 

 by Dr. Apjohn from Dr. Thomson. 



We shall now give a tabular view of the different results. 



are ridiculously erroneous, and would vitiate every investigation 

 on gaseous matter. The true quantities, computed from Ure'a 

 rule, are as follows : 



Specitic gravity of Gases standing over water at 6o°. 



Air .... 0.9909 



Oxygen 1.0995 



A/ote, .... 0.9636 



Chlorine .... 2.4653 

 Hydrogen, .... 0.07648 

 ♦ Answer, p. 2G8. 



+ Tableau de ta pesanteur specifique des gaXy et de quelquef tapeuri. Vol. 

 I. p. 383. 



J These quantities are taken, either from his late paper ou the moisture 

 of the gases, or computed from his formula. 



S Deduced from the numbers given at the end of the article, Gaa "^Die- 

 (unary of Chemittry. 



