292 
being the case. The ratio of the chloride of magnesium to 
the chloride of calcium is much greater, and of the chloride 
of sodium to the chloride of potassium, much smaller with 
Gmelin than with Dr. Apjohn. The quantities also of the 
bromide of magnesium and chloride of manganese, as deter- 
mined by Gmelin, are, asrespects Dr. Apjohn’s numbers, dis- 
proportionately great, and, what is very singular, the amount 
ofthe chloride of sodium obtained by Gmelin is absolutely less 
than that got by Dr. Apjohn, though the total amount of 
saline matter in the water examined by the former, is to that 
in the specimen examined by the latter, very nearly in the 
ratio of 4 to 3. 
It is not easy to explain such discrepancies, but assuming 
both analyses as correct, we arrive at the conclusion, that the 
waters of the lake in question are subject to a variation of 
constitution, affecting not only the relation of the saline 
matter to the water, but the proportions also which the 
different salts bear to each other. 
Mr. Bergin exhibited to the Academy, the results of 
some experiments with photogenic paper, prepared after the 
method of Mr. Talbot. 
Resotvep,—That the Academy do condole with the family 
of Dr. Perceval, one of the original Members of the Aca- 
demy, and its first Secretary; and that the Secretary be 
requested to draw up the expression of its condolence. 
ResotveD,—That the thanks of the Academy be given to 
the Marquis of Normanby for the manuscript of the late 
General Vallancey, presented by him to the Academy; 
and that the President be requested to communicate the 
same. 
