72 



THE NATURE AND 



[SECT. ii. 



In the absence therefore of proper experiments to ascertain the force of steam, 

 it is difficult to determine a rule that can be depended upon for high temperatures, 

 and we must now try to discover if the force of other vapours will afford any 

 further insight into the subject. 



OF THE ELASTIC FORCE OF THE VAPOUR OF ALCOHOL. 



104. The elastic force of the vapour of alcohol, or spirit of wine, has been 

 tried by several philosophers. The greater part of the experiments were made in 



At a temperature of about 770 Mr. Ivory's formula gives an elastic force equal to the 

 modulus of elasticity of water ; the steam would, if this were correct, be more dense than water ; 

 while La Tour found it required a space four times its volume to become steam at about the same 

 heat. Arsberger's experiments had not been seen by Mr. Ivory, or he would have had reason 

 for doubting the accuracy of M. Clement's observation ; but as it is quite unsupported either by 

 a description of the process, or any observations at other temperatures, its deviation in 

 excess both from formulae founded on a considerable range of experiments, and also from other 

 results, is to be regarded as a motive for doubt rather than for altering our formula. Mr. Ivory 

 most justly remarks, that this furnishes l< another instance of the great difficulty of detecting 

 general properties or laws by means of a comparison of particular results ;" and it is a difficulty 

 which ought to induce mathematicians possessed of such great powers as Mr. Ivory certainly is, 

 to endeavour to develope the first principles, rather than investigate a formula from experiments 

 alone. 



i M6canique Industrielle, vol. ii. p. 232. 



