1863.] 539 



or less influence such chemical actions as are accompanied by an 

 evolution of gas, so that it may cause a compound to be permanent 

 which otherwise would be decomposed*; but the results were for the 

 most part so indefinite and unconnected, or of such a character, that 

 Mr. Grove does not allude to the direct production of chemical action 

 from mechanical force. That this is, however, extremely probable 

 will be evident to all who have considered the manner in which the 

 various physical forces are correlated ; for if mechanical force can be 

 produced by chemical action, why should not the converse be true ? 

 In this paper I shall endeavour to show that such is really the fact, 

 and that in some cases the mechanical equivalent of the chemical force 

 may be determined. 



In order to obtain the necessary great pressure, I have made use of 

 a modification of the method employed by Bunsen ; but instead of 

 filling the tubes at the ordinary temperature of the atmosphere and 

 then gently heating them for several hours, I in the first instance filled 

 them at a temperature 10 or 20 C. lower, so that when finally 

 sealed up they contained considerably more liquid than they could 

 hold without pressure at the ordinary temperature of the atmosphere 

 at the time being ; and thus, by its tendency to expand, this liquid 

 and anything enclosed in the tube were subjected to a very great pres- 

 sure. By keeping the tubes in various parts of the house, according 

 as the weather varied, I have been able to maintain for several 

 weeks or even months a pressure of, for instance, about 100 atmo- 

 spheres, as measured by means of a capillary- tube pressure-gauge 

 enclosed within the larger tube. Since in all cases I had a second 

 tube which from first to last was treated precisely like the other, 

 pressure excepted, I have been able to determine the effect produced 

 by the pressure with very considerable accuracy at all events so as 

 to leave no doubt whatever about the general facts. At the same 

 time I wish it to be understood that the results described below mast 

 be looked upon only as approximations to the truth. 



* Sir James Hall, Trans. Roy. Soc. Edinb. 1812, vol. vi. p. 71. Wohler, Ann. 

 der Chem. und Pharm. vol. xxxiii. p. 125. Babinet, Ann. de Chim. et de Phys. 

 (2) vol.xxxvii. p. 183. Lothar Meyer, Pogg. Ann. vol. civ. p. 189. Beketoff, 

 Comptes Rendus, vol. xlviii. p. 442. Gassiot, Brit. Assoc. Report, 1854, p. 39. 

 Favre, Comptes Rendus, vol. li. p. 1027. Berthelot et Pean de Saint-Gilles, 

 L'Institut, 1862, p. 257. Gmelin's Handbook of Chemistry, published by the 

 Cavendish Society, vol. ii. p. 293, 



