THE CHEMICAL COMPOSITION OF LAKE WATERS 149 
mination, but is arrived at by difference, and represents the surplus 
acid required for neutrality after CI and SO^ have received their equiva- 
lent of bases. Organic matter is left entirely out of account in the 
analytical statements. Since of all possible combinations calcium 
carbonate is the one which is nearest its limit of solubility, it is a 
useful and not wholly misleading convention in interpreting analyses 
to pair off Ca with CO3 first of all, any surplus CO3 being regarded 
as combined with the alkali metals, and any surplus Ca with SO4. 
Lake of 
Geneva 
(Freundler).! 
Lake 
Cliamplain 
(Leighton).^ 
Lake 
Baikal 
(Schmidt).^ 
Lough 
Neagh 
(Hodges).^ 
Loch 
Baile a' 
Gliobhainn, 
Lismore 
(Tetlow).^ 
Dissolved matter : 
Parts per thousand. 
0-169 
0-067 
0-069 
0-155 
0-220 
/Ca. 
Mg 
Percent- Na 
age com- K . 
position of< CO3 
dissolved CI . 
matter. SO4 
SiOs 
V(AlFe)203 
27-8 
4-0 
1- 2 
0-9 
37-3 
0-6 
25-7 
2- 5 
trace 
21-2 
4- 2 
8-8 
45 -8 
1-8 
11-0 
5- 6 
1-6 
23-4 
3-5 
5- 8 
3-4 
49-8 
2-4 
6- 9 
2-0 
1-4 
17-7 
1-3 
15-4 
36-9 
5- 7 
10-7 
3-3 
6- 7 
38-5 
0-2 
0-3 
0-4 
58-2 
0- 9 
trace 
1- 2 
0-3 
The first three are examples of more or less normal waters, that 
of the Lake of .Geneva having a somewhat sulphatic tendency. In 
Lough Neagh there is excess of chlorine and of iron, due respectively 
to wind-blown salt from the sea, and to the passage of its affluents 
through peaty country. This w^ater and those of Lakes Champlain 
and Baikal are slightly on the alkaline side. The last analysis shows 
a typical hard water existing in a limestone country : the amount of 
dissolved matter is large, and it consists almost exclusively of calcium 
carbonate. As a Scottish loch water this is quite exceptional ; the 
mainland loch waters generally are exceedingly pure ; e.g. both for 
Loch Ness and Loch Katrine^ 0*029 part per thousand of total solids 
(organic included) are reported. Even purer are the Lake District 
waters, e.g. Thirlmere, with 0*020 part per thousand. 
1 Forel, Le Leraan, ii. p. 581, 1895. 
2 U.S. Geol. Survey, Water Supply Pcqjer 121, 1905, 
^ Bull. Acad. St Petersburg, xxiv. p. 423, 1878. 
^ Chem. News, xxx. p. 103, 1874. 
•5 Proc. Roy. Soc. Edin., xxv. p. 970, 1905. 
^ From an analysis of this notoriously soft water, kindly supplied by Mr F. W. 
Harris, City Analyst of Glasgow, it appears that carbonates are almost or entirely 
absent, whilst sulphates preponderate somewhat over chlorides ; calcium makes 
up 12 per cent, of the solids, and magnesium is reported in traces only. 
