208 



vero multum distant ab experimentis doctorum Deloroche 

 atque Berard, ad quae nostra propius accedunt ratione fliii- 

 dorum elasticorum elementariorum, experimenta D. Apjohn 

 ratione aerum compositorum." The opinion, however, here 

 expressed cannot, Dr. A. conceived, be considered as well 

 sustained by the numbers adduced by Suerman. Thus, to 

 give but a single example, the specific heat of hydrogen com- 

 pared to that of an equal volume of air, as deduced by 

 Suerman, was 1.3979, and as deduced, according to Suerman^ 

 by Dr. Apjohn. was 1,8948. Here is a material difference, 

 quite beyond the probable errors of experiment, in expla- 

 nation of which Dr.; Apjohn stated, that 1,8948, and the 

 other numbers attributed to him by Suerman, were, in 

 point of fact, not those which flowed from his experiments ; 

 and at the same time admitted, that when they were so con- 

 sidered by Suerman, he. Dr. A. himself, was in some degree 

 to blame. He had published his first results as the specific 

 heats of equal weights, when they were in reality the specific 

 heats of equal volumes ; but in arriving at them it was neces- 

 sary to be subjected to a particular correction^ which, howe- 

 ver, materially different in its influence upon them, according 

 as it is applied to the case of equal volumes or of equal 

 weights. Of these facts Suerman was not aware, and was 

 thus prevented from perceiving that the very close corres- 

 pondence which he recognized between the two series of 

 results amounted to an almost perfect identity. 



This identity, however, Dr. A. stated to be true of them 

 when viewed relatively but not absolutely. The direct de- 

 terminations by Suerman of the specific heat of air and of 

 the different gases, were. Dr. A. alleged, in every instance 

 greater than those at which he had arrived. This he attri- 

 buted to three causes: 1st. To Suerman's estimating the 

 caloric of elasticity of vapour higher than Dr. Apjohn had 

 done. 2nd. To his employing the formula of Gay-Lussac, 

 which differed from that which Dr. Apjohn had employed in 



