THE SALT DEPOSITS 207

be evaporated. As sea-water contains on an average 35
parts of salt per 1000, the evaporation of 1000 feet of seawater
 would deposit a layer which, if compact, would be
about 15 feet thick. If the basin were again covered by the
sea the magnesium and potassium chlorides of the upper
layer would be dissolved ; another 15 feet of salt per 1000 feet
of evaporated water might be laid down, and this process
of submergence and evaporation might go on indefinitely.
The evaporation of 30,000 feet of sea-water, the approximate
maximum depth of the oceans, would deposit only 450 feet
of salts. Yet some salt deposits are thousands of feet in
thickness.
CoNCENTRATION IN Sart Lakes—The deposits in an
inland sea (i.e. a sea completely cut off from the oceans)
that receives river-water containing bicarbonate of lime,
would contain precipitates of carbonate and sulphate of
lime; by this precipitation the sea-water would gradually
lose its carbonates and sulphates. Further evaporation
would precipitate the sodium chloride and the water would
be left as a bittern containing magnesium and potassium
chlorides, which might be deposited as carnallite (MgCl,
KCl, H,0). Such conditions may be illustrated by the Dead
Sea. The quality of the water poured into it from the
Jordan is shown by the analysis A; the composition of the
Dead Sea water is shown (B) from a sample from the depth
of about 600 feet, & miles from the northern end :—

Cl.
Br .
S50,
CO,
Na
K .
Ca .
Mg .
SiO, .
Salinity

Qa

414

7422
13°11
18-11
1-14
10°67
4-88
I-95
‘08 per cent.

B

67-84
I-75
oY

fr.
100
1-79
1-68
157

ti.
24 per cent.

All the carbonate and most of the sulphate of lime introduced
 from the Jordan is precipitated, and the Dead Sea water