INFLUENCE OF THE FOREST ON SPRINGS. 293 
Boussingault further states that the lakes of Switzerland 
have sustained a depression of level since the too prevalent 
destruction of the woods, and arrives at the general conclusion 
that, “in countries where great clearings have been made, 
there has most probably been a diminution in the living waters 
which flow upon the surface of the ground.” This conclusion 
he further supports by two examples: one, where a fine spring, 
at the foot of a wooded mountain in the Island of Ascension, 
dried up when the mountain was cleared, but reappeared when 
the wood was replanted; the other at Marmato, in the province 
of Popayan, where the streams employed to drive machinery 
were much diminished in volume, within two years after the 
clearing of the heights from which they derived their supplies. 
This latter is an interesting case, because, although the rain- 
gauges, established as soon as the decrease of water began to 
excite alarm, showed a greater fall of rain for the second 
year of observation than the first, yet there was no appre- 
eiable increase in the flow of the mill-streams. From these 
cases, the distinguished physicist infers that very restricted 
local clearings may diminish and even suppress springs 
and brooks, without any reduction in the total quantity of 
rain. 
It will have been noticed that these observations, with the 
exception of the last two cases, do not bear directly upon the 
question of the diminution of springs by clearings, but they 
logically infer it from the subsidence of the natural reservoirs 
which springs once filled. There is, however, no want of posi- 
tive evidence on this subject. 
Marchand cites the following instances: “ Before the felling 
of the woods, within the last few years, in the valley of the 
Soulce, the Combe-és-Mounin and the Little Valley, the Sorne 
furnished a regular and sufficient supply of water for the iron- 
works of Unterwyl, which was almost unaffected by drought or 
by heavy rains. The Sorne has now become a torrent, every 
shower occasions a flood, and after a few days of fine weather, 
the current falls so low that it has been necessary to change 
