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V. On the water of the Mediterranean. By William Hyde Wollaston, 
M.D. F.R.S. 
Read December 18 , 1828 . 
The object of the present communication is to do justice to the memory of 
my late friend, Dr. Marcet, by recording the result of one of his latest efforts 
in the cause of science. 
In his examination of sea-water, of which he gave an account in the Philo- 
sophical Transactions for 1819, the specimens with which he had been supplied 
from different depths in the Mediterranean, had not been sufficient to show 
what becomes of the vast amount of salt brought into that sea by the constant 
current which sets eastward through the Straits of Gibraltar. For though the 
escape of the water of that current may be fully accounted for by its evapora- 
tion, which must be very rapid and copious on the sunny shallows of Africa, 
yet the salt which that water held in solution, must remain in the basin of the 
Mediterranean, or escape by some hitherto unexplained means of exit. 
In the hope of obtaining a more abundant supply of water from the greatest 
accessible depths, especially near the Straits, he begged assistance from 
Captain William Henry Smith, R.N. who was engaged to make a survey of 
certain parts of that sea, and supplied that officer with the apparatus for 
raising water from great depths, which was contrived by Mr. Tennant, and 
is described in the communication already referred to. 
The zeal with which Dr. Marcet himself prosecuted his inquiries was so 
well known, that others were always willing to second his efforts, from a con- 
fidence that their labour would not be unprofitably wasted ; and Captain Smith 
did not fail to take every opportunity of collecting specimens in the course of 
his survey. But when he heard that Dr. Marcet was no more, not being 
aware of the interest with which the specimens would be received and exa- 
mined by many surviving friends, he was unfortunately but too ready to oblige 
