16 
Arterial Drainage 
those reservoirs, and in the periodical amount of rainfall and 
the regularity of its distribution. Many streams throughout the 
country, which formerly supplied large mills with unfailing 
water-power, except in the very driest of seasons, are now, with 
vastly improved machinery requiring less power, frequently 
unable to work ; and almost all are compelled to be supple- 
mented by steam-power to make good the deficiency. Owing 
partly to this cause, but principally to the modern system of 
drainage, by which the land is cleared of water almost as soon 
as it falls, having now none of the ancient reservoirs, in the 
shape of bogs and marshes, to receive and retain it for future 
use, all the old water millers complain that the rainfall, how- 
ever heavy, does them no permanent good. It just occasions 
a momentary flush, which is rather injurious than otherwise, 
being in excess of the requisite power, instead of being held in 
reserve by the marshes and, above all, by the subsoil of the 
adjacent land. This was formerly, in the undrained state of 
the country, perhaps the largest source of supply, because it 
extended over the whole area, and yielded its reserve de- 
liberately and in driblets." The proportion of forest or wood- 
land required for an agricultural country, in order to insure a 
regular and sufficient rainfall without violent storms, is estimated 
at 23 per cent, for the interior, and 20 per cent, near the coast. 
This estimate relates to Germany ; but in England the proportion, 
according to Sir Henry James, the late head of the Ordnance 
Department, is only 2^ per cent. " The Wolf Spring in the 
Commune of Soubey, in France, furnishes a remarkable instance 
of the influence of woods upon springs. A few years ago this 
spring did not exist. At the place where it now rises a small 
thread of water was observed after very long rains, but the stream 
disappeared with the rains. The spot is in the middle of a very 
steep pasture, inclining to the south. Eighty years ago, the 
owner of the land perceiving that some firs were shooting up in 
the upper part of it, determined to let them grow, and they soon 
formed a flourishing grove. As soon as they were well grown, 
a fine spring appeared in place of the occasional rill, and fur- 
nished abundant water in the longest drought. For forty or 
fifty years this spring was considered the best in CIos-du-Doubs. 
A few years since the grove was felled and the ground turned 
again into a pasture. The spring disappeared with the wood, 
and is now as dry as it was ninety years ago." Numerous other 
instances could be quoted to show that the felling or plantitig 
of timber has a most material influence on the rainfall and 
springs of a country, and also in ameliorating the conditions of 
climate. Woods are almost always moist, for not only is eva- 
poration checked by the shade of the foliage, but the trees them- 
