432 The Water Economy of France 
Analysis of a Litre of Seine Water, = to 1*7G0773 Pint. 
Matter Contained in the Water. 
Ivry. 
Notre Oame. 
Gros Caillou. 
Chaillot. 
Gaseous Matter. 
Pints. 
Pints. 
Pint.-. 
Pints. 
Free carbonic acid gas 
0-005 
0-023 
0-005 
0-024 
0-007 
0-024 
0-005 
0-023 
Solid Matter. 
Grains. 
Grains. 
Grains. 
Grains. 
Bicarbonate of magnesia . . 
Sulphate of magnesia . . . . 1 
Sulphate of soda J 
Chlorate of magnesium .. ..) 
Chlorate of sodium ) 
Salts of potash 
Silicic acid, alumina, and oxide) 
2-037 
0-925 
0-308 
0-154 
0-155 
traces 
slight traces 
0-124 
traces 
2-685 
0-938 
0-612 
0-262 
0-386 
traces 
slight traces 
0-224 
traces 
3-534 
1-157 
0-617 
0-417 
0-494 
traces 
f slight but "1 
1 clear traces j 
0-355 
3-549 
1-173 
0-687 
0-355 
0-494 
traces 
j slight but \ 
jclear tracesj 
0-378 
Total 
3' 703 
5-107 
6-574 
6-666 
Further researches made by MM. Girai-din and Preisser have 
brought to light another phenomenon, no doubt common to all 
rivers similarly situated with the Seine, namely, that a large pro- 
portion of the mineral salts absorbed by the river on its passage 
through Paris are precipitated on its way down to Rouen ; for 
the Seine water at Rouen was found to contain a less proportion 
of mineral matter than on its exit from Paris. This difference 
relates principally to silicic acid and- carbonate of lime. On the 
other hand, MM. Bobierre and Merode have found that the 
waters of the Loire contain a less proportion of mineral com- 
pounds of silicic acid with aluminium and other bases, below, 
than above the city of Nantes ; whilst organic matter and cal- 
careous salts have sensibly increased. The explanation of the 
latter phenomenon is found in the hypothesis, that such sub- 
stances as silicate of alumina held suspended by the waters of 
the Loire are precipitated during the passage of that river through 
the town, owing to the many obstacles which break the velocity 
of the stream within the harbour, and thus allow such salts to 
settle down. The increase in calcareous salts is easily accounted 
for by the afHuence of the river Erdre, which is strongly impreg- 
nated with them. Nevertheless this phenomenon exhibits a 
remarkable contrast to what has been observed in the Seine, 
