SUMMARY OF RESULTS. 
The foregoing memoir, though ostensibly only a report on a series of investigations 
into the composition of ocean-water, which it has been my privilege to carry out under 
the auspices of the Director of the Expedition, includes also the final elaboration of all 
Mr. Buchanan’s work connected therewith, and is, consequently, a complete record of 
what the Challenger Expedition has added to our knowledge on the subject. But the 
greater part of my paper consists of more or less lengthy discussions of chemical methods 
and matters of calculation, which, as mere means to an end, are of little interest to the 
general reader, and may prove tiresome even to the scientific critic, if he do not happen 
to be a professional chemist. 
This is my reason for drawing up the following summary, in which I have 
endeavoured to collect the general results of the whole investigation, and, for the 
benefit of non-professional readers, to explain their oceanographic significance. 
The configuration of the ocean, broadly speaking, must have been the same as it is 
now for thousands of years. Hence its bed may be regarded by this time as having 
been almost deprived of all the more soluble components. No mineral, it is true, is 
absolutely insoluble in water ; the ocean, consequently, must still be presumed to 
continue taking up soluble matter from the volcanic and other minerals with which it is in 
contact on the floor of the ocean, and what it thus gains is probably in excess over what 
it contributes towards the matter of new deposits. It must be granted also that it is 
continuously taking in large masses of dissolved mineral matter from rivers, and that 
what it receives from these two sources in a single year, if measured by ordinary 
standards, amounts to an immense quantity. But the gain even in a century is a 
mere trifle in comparison with what it already contains, — far less no doubt than the 
relative errors in our most exact methods of measurement. 
The ocean, of course, takes in gases from the air as well as solids from the earth’s 
crust ; but this is a case of mutual exchange, in which the gain and loss, on either side, 
must long since have arrived at a state of equilibrium. 
Hence the absolute composition of the ocean as a whole, meaning the total number of 
kilograms of water, chloride of sodium, &c., &c., present in it, though subject probably 
to an extremely slow increase in the dissolved saline matter, is practically constant and 
