NARRATIVE OF THE CRUISE. 
97 5 
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 (CCh) 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 
grammes, corresponds to 2 '78 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 0*140 to 0*1 04, 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 O'l 40 to 
0T48 occur preferably in surface waters, while from 0*148 to 0T60 the bottom waters 
were in the majority. From a graphic representation 1 showing the frequency of occur- 
rence of certain narrow ranges of alkalinity, I concluded that the most frequently 
occurring value is 
For surface waters, ....... 0446±0 - 002 
For bottom waters, ....... 0 - 152±0 - 003 
which values may lie adopted provisionally , for the two kinds of ocean water. In 
fifteen cases I was in a position to compare with one another the alkalinity of a surface 
water and the bottom water at the same Station. In two cases the balance was in favour 
of the surface water, the numbers being CFO 15 and O'OIO respectively; in one case 
the difference was nil; in the remaining twelve cases it was in favour of the bottom 
water, the differences ranging from 0*002 to 0*019. According to the above two averages 
the alkalinity of bottom water exceeds that of surface water by 0*00G, meaning of course 
0'00G grammes of carbonic acid per 100 grammes of total salts, or 0*014 grammes of lime 
OaO per 100 of chlorine, if we assume the increase in alkalinity to be owing to additional 
lime. My determinations of the lime, as stated, had shown the presence of 0*013 grammes 
of extra lime in deep-sea as compared with shallow waters. The closeness of the agree- 
ment is of course accidental. That the surplus base in a sea water is not owing entirely to 
carbonate of lime is too obvious to be specially pointed out. In sea water (as in any 
mixed salt solution) each base is combined with each acid, and as there are four acids 
and four bases there must be sixteen salts, the individual percentages of which we have 
no means of' determining. But there are reasons for assuming that the carbonic acid 
1 See Diagram, Pliys. Chevn. Chall. Exp., part i. p. 136, 1884. 
(XARR. CHALL. EXP. VOL. I. — 1885.) 
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