296 THREE CRUISES OF THE “ BLAKE." 
of known strength, and driving off the liberated carbonic acid 
by boiling gently and collecting it in baryta water of known 
strength, the amount of acid neutralized will give the carbonic 
acid present as neutral carbonate; the quantity of baryta neu- 
tralized will give the total amount of carbonic acid. 
More than thirty elements are known in solution in ocean- 
water, but in such minute quantities that no attempt can be 
made to determine them from small samples. Forchhammer’s 
memoir dealt with surface water only ; but he stated that the 
percentage of the salts of the sea-water was the same in all 
parts of the ocean. Dittmar extended this, and proved that in 
depth also the composition was subject to but one exception : 
the proportion of lime was larger in very deep water than near 
the surface. 
Professor Dittmar, in his admirable Report on the samples of 
sea-water collected by Dr. Buchanan, the chemist of the “ Chal- 
lenger,” gives the following analyses as the average composition 
of ocean-water salts : — 
“Chlorine. | ; : ; à ў 52.292 
Bromine i Д ; { ў . 0.1884 
Sulphuric acid . i ; ў Я Я 6.410 
Carbonie acid j i " Р И i: Ө 152 
Lime 1 ; ; x , , i А 1.676 
Magnesia, 5 i a à ‚ ‘ . 6.209 
Potash À Laur > ; А А j 1.339 
Soda ^ a ; : i : i ‚ 41,284 
(Basic oxygen, equivalent to halogens) ‚ (—12.493) 
Total Salts ‹ ч . 100.000 
“Giving the following as the average composition of sea-water : — 
Chloride of sodium . t 6 j i 77.758 
Chloride of magnesium . | i Й . 10.878 
Sulphate of magnesium 4 í i { 4.787 
Sulphate of lime  . ? А ; ; . 8.600 
Sulphate of potash . ; : ; : 2.465 
Bromide of magnesium . i И y e 24 tg 
Carbonate of lime : s ` : Т 0.845 
Total Salts à 1 . 100.000 ~ 
1 The amount of lime is as 10,000: 247 in the West India seas, and as 
10,000 : 371 in the Baltic. 
