Progress of Foreign Science. 3 1 1 



and M. Dulong, two of the most distinguished chemists on the 

 Continent, in the sequel of their late elaborate memoir on the 

 specific gravity of some elastic fluids *, speak of Dr. Prout's 

 speculations in the following words :-—" Before concluding we 

 shall observe, that the new determinations, which we now 

 present, differ little from those which are to be found in an 

 anonymous memoir, printed in the Annals of Philosophy, 

 for November 1815, and February 1816. But the English 

 author has made no experiments, and the hypotheses, which he 

 employed to correct his adopted numbers, being absolutely 

 gratuitous or false, his results could not inspire any confi- 

 dence." This we consider as a harsh and unjustifiable criti- 

 cism. Can any thing be a better proof, that the hypotheses 

 were not o-ratuitous and not false, than that after the progres- 

 sive investigations of five years, two French chemists, by ap- 

 plying the most refined and rigid methods of experiment, should 

 arrive at precisely the same results, which the English author 

 had theoretically deduced ? 



II. Caloric. — The principal paper on this subject, which 

 has recently appeared on the Continent, is that of M. Navier, 

 Professor of Practical Mechanics in the Ecole des Fonts et 

 Chaussces of Paris ; and ii is entitled, " Note on the Mechani- 

 cal Action of Combustibles t." Several writers have endea- 

 voured to establish a comparison between the mechanical ac- 

 tions, capable of being produced by the same weight of a com- 

 bustible, employed to vaporize water, and to heat atmosphe- 

 rical air. It has been advanced, that the latter process, mak- 

 ing allowance for the variable causes of lo?s which occur in 

 machines, might be more advantageous than the former. Se- 

 veral artists have endeavoured to construct machines on this 

 principle t- 



In the calculations presented on this question, there exists a 

 cause of error, which has been remarked by M. M. Clement 

 and Desormes, in a memoir presented to the Academy of 

 Sciences, in 1820, but not yet printed. The authors of those 

 calculations had not taken into account, the quantity of heat 

 which the air absorbs, when it dilates, without changing its 

 temperature. Mr. Navier takes for his unity of heat the 

 quantity necessary to raise by 1° C, the temperature of a ki- 

 logramme (about 2| pounds avoirdupois) of water in the liquid 

 state ; this unity he styles a decjrec of heat. The number of de- 

 grees of heal necessary to raise by 1°, the temperature of 1 



* Annalef dc Chhnir rl ile Vliysiqui. torn. xv. p. .I8fi. 



f lliiil. torn. xvii. |). 3.')7. 



J I!y far the most ingenious i)f these is tlic heated air-etifjinc, for which 

 .1 pali'iit was, a few years l)ack, granted to the Rev. Mr. Sterling, of 

 Kilinuraock. Of this wc shall give a short account iu a future Nuinher. 



