270 



In the present communication, I shall merely mention the results 

 obtained, without entering at all upon the details of the experiment. 



I found that a pressure of, as nearly as I have been able to esti- 

 mate it, 8*1 atmospheres produced a depression measured by 7^^ 

 divisions of the tube, on the column of ether in the thermometer ; 

 and again, a pressure of 16-8 atmospheres produced a thermometric 

 depression of 16^ divisions. Hence the observed lowering of tem- 

 perature was r; or -106° F. in the former case, and -p or -232° F. 



in the latter. 



Let us compare these results with theory. According to the con- 

 clusions ai'rived at by my brother in the paper referred to above, the 

 lowerintr of the freezing-point of water by 8-1 atmospheres of pres- 

 sure would be 8-1 x "OISS, or -109° F. ; and the lowering of the 

 freezing-point by 16-8 atmospheres would be 16-8 x '0135, or 

 •227^ F. Hence, we have the following highly satisfactory compa- 

 rison, for the two cases, between the experiment and theory. 



It was, I confess, with some surprise, that, after having completed 

 the observations under an impression that they presented great dis- 

 crepancies from the theoretical expectations,! found the numbers I had 

 noted down indicated in reality an agreement so remarkably close, 

 that I could not but attribute it in some degree to chance, when I 

 reflected on the very rude manner in which the quantitative parts of 

 the experiment (especially the measurement of the pressure, and the 

 evaluation of the division of the ether thermometer) had been con- 

 ducted. 



I hope, before long, to have a thermometer constructed, which 

 shall be at least three times as sensitive as the ether thermometer 

 I have used hitherto ; and I expect with it to be able to perceive 

 the effect of increasing or diminishing the pressure by less than an 

 atmosphere, in lowering or elevating the freezing-point of water. 



