292 M. de la Tour on the [April, 



Until these doubts are removed by new experiments, it appears 

 that we may recapitulate what has been stated in the following 

 conclusions : 



1. That alcohol of specific gravity 0-817, oil of petroleum of 

 specific gravity 0-807, and sulphuric ether, submitted to the 

 action of heat and compression, are susceptible of being com- 

 pletely reduced to vapour under a volume rather exceeding 

 twice that of each fluid. 



2. That an increase of pressure occasioned by the presence 

 of air in several of the experiments which have been described, 

 occasioned no obstacle to the evaporation of the fluid in the 

 same space, that it merely rendered its expansion more quiet 

 and more easy of observation until the moment in which the 

 fluid suddenly disappeared. 



3. That water, although undoubtedly susceptible of being 

 reduced to very compressed vapour, could not oe subjected to 

 complete experiments for want of sufficient means to close the 

 compressing instrument perfectly, as well as that it alters the 

 transparency of glass tubes by combining with the alkali which 

 enters into their composition. 



I have presumed that this notice would particularly interest 

 those who are concerned in the use of steam-engines, and also 

 probably furnish some slight indications for the solution of the 

 question relating to the compressibility of fluids, lately proposed 

 as a prize subject by the Institute ; it is this which determined 

 me to present it to the class, my chief ambition being to prove, 

 that I desire to render myself more and more worthy of the 

 favourable reception which it has bestowed upon my former 

 labours. 



Supplement to the preceding Memoir. 



I have attempted to determine the pressure which ether and 

 alcohol exert at the moment in which these fluids are suddenly 

 reduced to vapour. The method I adopted was the following : 



Exper. 1. — 1 took a tube, abc (see fig. next page), of the most 

 even bore I could obtain, the interior diameter of which was one 

 millimetre ; I united it to the tube def; the internal diameter of 

 which was about 4^- millimetres. The apparatus then resembled a 

 syphon barometer. The two ends, a and J) remaining open, 

 mercury was first introduced, and afterwards sulphuric ether. 

 The mercury occupied the space bed e, and the ether the space 

 ef; by inclining the apparatus, it was easy to alter the level of 

 the mercury so as to fill the space ba ; by these means it was 

 ascertained that a variation of one millimetre in the large tube, 

 caused a variation of 20 millimetres in the smaller one ; a propor- 

 tion which was judged sufficient for the graduation required. 

 The space b a is that which the mercury may occupy, when its 

 level e in the large tube is sunk to the point d, the length a b is 



