of sea waters , in different parts of the ocean , &c. 199 
This total amount, it may be observed, does not exactly cor- 
respond with the saline residue of 21,3 grs. obtained by evapo- 
ration from 300 grs. of the water ; but it should be remem- 
bered that this residue was dried at 212 0 only, which, with 
some salts, produces a considerable difference. I thought 
it important to ascertain the amount of this difference by 
direct experiments; and I found that 100 grs. of muriate 
of lime dried at 212 0 , were reduced by ignition to 61,9 ; so 
that if 100 grs. of muriate of magnesia, dried at 212 0 , be sup- 
posed to be brought to a state of perfect dryness, they will 
be reduced to 52 grs. As to the muriate of soda and sulphate 
of soda, when well dried at 212 0 , they lose no sensible weight 
by being ignited. 
Upon making due allowance for the moisture contained in 
the two earthy muriates, according to the estimates just 
mentioned, we shall find the above result altered as follows : 
Muriate of soda 
13,3 
Sulphate of soda - 
2,33 
Muriate of lime 
Muriate of magnesia 
4-955 
21,460 
Which result closely corresponds with the saline residue 
obtained by evaporation, which was 21,3 grs. 
It remains for me in concluding this paper, to communicate 
to the Society an interesting fact on the composition of sea 
water just discovered by Dr. Wollaston, and which it is no 
small gratification to me to think that the present inquiry has 
been the accidental means of bringing to light. As I was 
beginning the chemical part of this investigation, Dr. Wol- 
