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, as respects Dr. Apjohn's numbers, dis- 

 proportionately great, and, what is very singular, the amount 

 of the 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. 



Resolved, — 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. 



Resolved, — That the thanks of the Academy be given to 

 the Marquis ofNormanby for the manuscript of the late 

 General Vallancey, presented by him to the Academy; 

 and that the President be requested to communicate the 

 same. 



