252 Obituary Notices of Fellows deceased. 



The results of very careful determinations of the refractive index of 

 water between these limits of temperature show that the refractive 

 index increases continuously, with diminution of temperature, down 

 to the freezing point, as stated by Jamin ; but that the rate of increase 

 changes at about 4, the temperature of the maximum density of water, 

 as had been already surmised by Gladstone and Dale. 



Conroy's last memoir was a contribution to the " Proc. of the 

 Eoyal Society" in 1899 (p. 308) "On the Eefractive Indices and 

 Densities of Normal and Semi-normal Aqueous Solutions of Hydrogen 

 Chloride and the Chlorides of the Alkalies." The work consisted of 

 very careful determinations of these physical constants at the uniform 

 temperature of 18. The results are recorded in a table, from which 

 it is clear that both the densities and the refractive indices increase 

 with the molecular weight of the substance in solution, except in the 

 case of potassium chloride, whose refractive index is slightly lower 

 than that of sodium chloride. 



In all these researches three things stand out clearly as expressive 

 of Conroy's method of work namely, the extreme delicacy and 

 neatness of his experimental manipulation, the endeavour to attain 

 the highest accuracy in numerical results, and the lucidity and brevity 

 of the exposition of the conclusions derivable from his researches. 



A. V. H. 



