ACKROYD : OX THE CIRCULATION OF SALT. 
419 
of common salt in solution ; and the Dead Sea, on the other hand, 
with magnesium salts in excess from the excessive evaporation, may 
be continuously precipitating its salt, giving us in the southern parts 
" quite a paste ' (Tristram), while on the floor of the lake itself salt 
is being deposited (Hull : Geol. and Geog. of Arabia Petrsea, p. 122). 
Herein I take it lies the explanation of the origin of salt hills, like 
Jebel Usdum, which have always been a mystery to geologists. 
The Lost Iodine. 
A final objection to the theory that the Dead Sea owes its salt- 
ness largely to transport-ed sea-salt is that of the absence of iodine 
in its waters. How far this objection is a legitimate one is a matter 
for serious consideration. Its absence, seeing that it occurs in such 
minute quantity in the ocean — a few parts per million — is not so 
wonderful as that of the loss of CO.^ which has entered the Dead 
Sea in combination with lime from the limestone hills of Palestine, 
and yet gives practically no evidence of its presence in its waters. 
It may be that the iodine has similarly vanished in some occult chemical 
change which remains to be discovered. Another possible view is 
that the iodine has not been found and not that it is not there. The 
difficulties of detection are many, arising not only from the minute 
quantity of it. but also from its state of combination. Sonstadt 
regarded it as existing as iodate in sea-water, a form that would elude 
the ordinary tests for iodides. Gautier also has come to the con- 
clusion that the iodine in sea-water is not in the form of metallic 
iodides, but that it exists in organic compounds, four-fifths of it being 
soluble, and the remaining fifth forming part of the substance of 
the infusoria inhabiting the superficial layers of the ocean (Comp. 
Rend., 1809, 128, 1,009—1,075). Finally it exists there with a 
prodigious excess of other haloid compounds, which increase the 
difficulties of detection and separation. These considerations lead 
one to think that the presence or absence of this element in the Dead 
Sea or its deposits is still a question for investigation, in which the 
modern methods of chemical science could possibly be now effectively 
employed. In the meantime any arguments founded on its supposed 
absence have very little value. 
