in its relation to AfjricuUuic. 
direction, then suddenly bends to the noidi, and reaches the; 
schistose and eoal-nieasure formations of Hainault and Ardennes. 
From Maastricht to the sea, it flows over tertiary deposits. 
Of the north-west or Seine basin, the central portion is well 
defined, and has received the name of th(! tertiary Parisian basin. 
It is surrounded by a remarkably rejii^ular barrier of Jurassic 
hills, whose strata, uniformly outcropping each other in an 
eccentric direction, encircle concentrically the various strata of 
the cretacean formation. In the west, its limits are formed by 
the elevated and uniform plateau of Beauce, which divides it 
from the basin of the Loire. 
Among the principal affluents of the Seine on its right bank, 
the Aube, like the Marne and the Meuse, springs from the 
Jurassic plateau of Langres ; the Marne, in a course of about 
330 miles, runs from its source to St. Dizier through the Jurassic 
formation, from St. Dizier to Epernay through the greensand and 
chalk ; and finally through tertiary strata down to its conflu- 
ence with the Seine at Charenton. The Oise chiefly derives 
its supplies from the Jurassic plateaux. On the left bank, the 
Yonne has its source in the porphyritic and granite heights of 
Morvan, and brings the waters from those primitive formations ; 
and lastly, the Eure flows from the calcareous plateaux of Beauce. 
Thus it will be seen that, with the exception of the Yonne, the 
Seine itself and all its tributary streams flow over calcareous strata. 
The importance of the river Seine to so large a population as 
that of Paris, has naturally drawn the greatest attention of 
chemists to the nature of its waters and that of its affluents. I 
will only select out of the numerous analyses which have been 
made, such as present an interest to English agriculture. The 
results of the researches made by MM. Boutron and Henry, 
show the various matter contained in the Seine water before its 
entrance into Paris, at two points of its passage through the city, 
and at its exit. 
This analysis (page 432) is suggestive of many important con- 
clusions as regards the physical modification which the waters 
of a river undergo in their passage through a town. Thus it is 
found that the quantity of bicarbonate of lime, sulphate of lime, 
alkaline azotate (or nitrate), and organic matter, singularly 
increases as the stream flows through the city of Paris. But if 
so sensible a progression in the quantities of mineral and organic 
matters is noticeable in the river Seine, which after all receives 
but a comparatively small proportion of the sewerage of Paris, 
where houses have few or no cesspools connected with sewers, 
how vastly greater must be that increase in the river Thames, for 
instance, from its approach at Putney to its exit at Greenwich, 
receiving as it does the offal of so vast and populous an area ! 
