ACKKOYD : ON THE CIKCULATION OF SALT. 
407 
it has been separated by clianges in physical geography ; it was 
then Salter than at present, but is now growing Salter again every 
year, and the fauna now inhabiting its waters have likewise con- 
siderable affinities with North Sea types."' Now I should tliink 
the whole physical facts of the case are comprised in the simple state- 
ments that the Caspian is an inland sea of large volume and variable 
■composition, fed by inland rivers rising in and flowing through regions 
where the sea-salt in the rainfall, not reckoning that derived from 
the lake itself, must have reached a minimum ; where the chief 
source of saltness must be the earth-salt from solvent denudation, 
and how small that may be expected to be will be presently shown 
in the case of the Aire at Malham Cove ; where a large portion of 
the evaporated water must come down again to the sea itself, so large 
is its area ; from all of which statements it follows that the Caspian 
must increase in saltness at so phenomenally slow a rate that one is 
not surprised to find it least salt of all the waters which have been 
mentioned. As an inland lake without outlet, one would think 
that it can never have been Salter than it is at present, and it will 
be well to revise the biological data upon which such an idea is based. 
Let us next consider the Dead Sea from this point of view. Little 
further removed from the Mediterranean than Widdop is from the 
Irish Sea, ^vith a rainfall in Palestine higher than that of the Peninne 
Hills, and an intensity of meteorological conditions in the past of 
which we can at the present day form but a poor conception,"^ it 
is reasonable to suppose that the salts in the Dead Sea have been 
for the most part derived from the Mediterranean— carried by winds 
and brought down by rains — and, barring the contributions of Jebel 
Usdum, it will probably be found that over 90 per cent, of the salts 
€ome from this source. On such a theory we look for some measure 
of likeness between the dissolved matters of the two waters, but an 
initial obstacle to comparison presents itself in the much greater 
concentration in one case than in the other, and in the variability 
of the Dead Sea itself from the North, where the Jordan enters, to 
the South, where the salt hill of JebeJ Usdum overlooks it. In 
* The Land of Israel, Tristram, p. 320. 
