REPORT ON THE COMPOSITION OF OCEAN-WATER. 
61 
dilatometers, the temperature in all cases being defined by means of special thermometers, 
d haute precision. It is this latter circumstance more especially which induces me to 
think that whatever may be the degree of precision with which I succeeded in formulating 
the relation ^=/(S, t ), they came nearer the truth than I did in determining the relation 
for a given kind of sea- water between temperature and volume. I very much regret that 
Thorpe and Rucker did not supplement their masterly research by the determination of 
the salinities (the y’s) of their waters, so that I could have utilised it for checking the 
constants in my formula, and thereby my reductions of Buchanan’s “ specific gravities at 
the temperature of observation ” to terms of y. I hope that Messrs. Thorpe and Rucker 
have preserved samples of their sea-waters, and will one clay carry out the supplementary 
chemical work which I suggest. Meanwhile their results afford to me an excellent means 
for criticising what my formula contains of the S —f (t) element. 
In the following Table III., Columns II., III., and IV. give the relative volumes, at 
the temperatures named in Column I., of a sea- water whose y=19 , 39, which I calculate 
to be the value appertaining to Ekman’s water “ D,” according to the authorities named 
in the columns’ headings. Column Y. gives the volumes assigned by Thorpe and Rucker 
to their water “ B.” In Column VI. follow Hubbard’s relative volumes of “average 
ocean-w r ater.” The two last columns refer to the salinity (y=17‘09) of Thorpe and 
Rucker’s water “ C.” Column VII. gives their values ; Column VIII. the corresponding 
values demanded by my formula. The numbers under “ Ekman ” are transcribed from 
his table in the Norwegian memoir ; those under “ Hubbard ” are the entries in 
Buchanan’s Centigrade edition of Hubbard’s table, divided by the there given relative 
volume at 0° C. The numbers given as “ Thorpe and Rucker’s ” are extracted from Table 
XIY. of their memoir. This table gives the relative volumes of their vnters A, B, C, and 
D at 0°, 2° . . . 12°, 15°, 18° . . . 36°. From this table I deduced what I needed of volume- 
values for 5°, 20°, and 25° by interpolation by first and second differences. This sufficed 
for my Columns Y. and VII. The numbers in Column IV. were obtained by what I may 
call horizontal interpolation between corresponding values for B and C, based on the 
assumption that taking V as a general symbol for the volumes (of A, B, &c.) at a given 
temperature, and S 0 as designating their result for the specific gravity at 0’ C., — ^ 
is a constant. I had no difficulty in satisfying myself that this assumption does hold for 
their results with a sufficient degree of approximation. 
I may here state, in passing, that according to a series of calculations which I made 
(but had no time to check, and simply put aside), this proposition, or rather the almost 
identical assertion that (at t°) is a constant, does not hold for Ekman’s results with 
' AW 
his waters A, B, C, D. This may be owing either to the fact that the relation as a 
matter of physical law ceases to hold at salinities as low as those of his water A, 
