THE CHEMICAL COMPOSITION OF 
LAKE WATERS 
By W. a. CASPARI, B.Sc, Ph.D., F.I.C. 
(Assistant to Sir John Mnrray, K. C. B. ) 
Comparatively few of the world's lake waters have been submitted 
to chemical examination. As a rule, only the more highly saline and 
abnormal waters are analysed for the interest of the thing. Analyses 
of ordinary waters are seldom undertaken except to test their 
potability, or with reference to their industrial application ; but 
nearly all potability analyses, and many industrial analyses, are in- 
complete and of little use to the limnologist. On the whole, 
however, a fair number of full analyses of lake and river waters have 
by now been accumulated. Sufficient data being thus at hand, it 
may here be expedient to review briefly what is known, from the 
chemical standpoint, about the waters of inland lakes. 
In discussing the chemistry of lacustrine waters we have to 
distinguish sharply between two types of lakes, viz. those which 
discharge into an outflow, and those which form the terminus of a catch- 
ment area. The vast majority of lakes belong to the former type ; 
they are filled with continuously renewed water, and act, as it were, 
as temporary reservoirs of the system of rivers flowing into them. 
As regards chemical composition, the water of such a lake will 
represent an average, or rather an integral, of the waters of its 
affluents ; the additional matter brought into solution from the bed 
and sides of the lake itself is of vanishing importance, because the 
area of land acted upon is small (as compared with river conditions) 
in proportion to the bulk of water, and because there is little or no 
mechanical erosion in a lake, except within the sphere of wave-action 
around the shore-line. There is thus no difference in principle 
between lake water and river water, provided the lake be not a 
terminus. Ultimately the water of a given lake will depend, for its 
chemical composition, on the nature of the country traversed by the 
rivers which feed it. 
At all points of its course, a river receives contributions of 
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