REPORT ON THE COMPOSITION OF OCEAN-WATER. 
205 
In deep-sea waters — 
Mixture III., 
In surface waters — 
Mixture I., 
Difference, 
In medium depth waters- 
Mixture II., 
In surface waters, 
Difference, 
3-0307 
3-0175 
0-0132 
3-0300 
3-0175 
0-0125 
and either of the two differences is five to six times as great as even the absolute sum of 
the probable errors of the respective two terms. A discussion of the quantities of lime 
brought out by the 77 analyses had given a similar result, but exaggerated the difference 
between deep-sea on the one hand and shallow or medium depth on the other. 
But there can be no doubt that, if I had applied even as exact a method in the 77 
analyses as I did subsequently in the special investigation on the lime, I should have 
arrived at a greater difference than 0'013 between certain individual samples. 
The result under discussion received a valuable confirmation from the alkalinity 
determinations to which I had occasion to refer above. Following the example of the 
Norwegian chemists, I measured the surplus base (i.e., the base left unsaturated by the 
sulphuric and hydrochloric acid) by the weight of carbonic acid (C0 2 ) which it would need 
to convert it into normal carbonate, and referred it to 1 litre of water analysed. But 
it struck me that in discussing any series of such determinations, they must be referred 
to a constant salinity, and I accordingly reduced all my numbers to 100 parts of total 
salts or 5 5 '42 of halogen counted as chlorine; so that with me “alkalinity,” as designating 
a quantity, means “the weight of carbonic acid (C0 2 ) present as normal carbonate (i.e., 
in forms similar to carbonate of lime) in every 100 parts of total salts,” which, on an 
average of 130 cases, and if the number of parts by weight of carbonic acid be taken in 
grams, corresponds to 2 "7 8 litres. Omitting a number of abnormally high or low values, 
and a few suspected analyses, which left 130 cases for discussion, I found the alkalinity 
in the whole set to range substantially from 0T40 to 0T64, and then, confining myself to 
“surface” waters (meaning waters from depths not exceeding 100 fathoms) and bottom 
waters, and referring on both sides to 100 samples, I found that alkalinities from 0T40 to 
0T48 occur preferably in surface waters, while from 0T48 to 0T60 the bottom waters 
were in the majority. From a graphic representation * showing the frequency of occur- 
rence of certain narrow ranges of alkalinity, I concluded that the most frequently 
occurring value is 
0-146 ± 0-002 
0-152 + 0-003 
Eor surface waters, . 
Eor bottom waters, . 
* See diagram on p. 130. 
