200 INFLUENCE OF THE FOREST ON SPRINGS. 
ping of this stratum, it bursts from a hillside as a running 
spring. But such instances are doubtless too rare to form a 
frequent or an important exception to the general law, because 
it is only under very uncommon circumstances that rain water 
runs off over the surface of forest ground instead of sinking 
into it, and very rarely the case that such a soil as has just 
been supposed is covered by a layer of vegetable earth thick 
enough to retain, until it is evaporated, all the rain that falls 
upon it, without imparting any water to the strata below it. 
If we look at the point under discussion as purely a ques¬ 
tion of fact, to be determined by positive evidence and not by 
argument, the observations of Boussingault are, both in the 
circumstances they detail, and in the weight of authority to 
be attached to the testimony, among the most important yet 
recorded. They are embodied in the fourth section of the 
twentieth chapter of that writer’s ficonomie Hurdle , and I have 
already referred to them on page 191 for another purpose. 
The interest of the question will justify me in giving, in Bous- 
singault’s own words, the facts and some of the remarks with 
which he accompanies the details of them: “In many local¬ 
ities,” he observes,* “ it has been thought that, within a certain 
number of years, a sensible diminution has been perceived in 
the volume of water of streams utilized as a motive power; 
at other points, there are grounds for believing that rivers 
have become shallower, and the increasing breadth of the belt 
of pebbles along their banks seems to prove the loss of a part 
of their water; and, finally, abundant springs have almost 
dried up. These observations have been principally made in 
valleys bounded by high mountains, and it is thought to have 
been noticed that this diminution of the waters has imme¬ 
diately followed the epoch when the inhabitants have begun 
to destroy, unsparingly, the woods which were spread over the 
face of the land. 
“These facts would indicate that, where clearings have 
been made, it rains less than formerly, and this is the gener- 
* Economie Rurale , p. 730. 
