MISCELLANEA. 
189 
plifying the subject we can dismiss it with a few remarks — 
this is the subterranean water level ; but our attention in the 
first instance at all events is directed to the surface drainings^ 
and therefore^ was it for this reason only_, the question of 
subterranean waters would be set aside for the time ; the 
more important reason,, however, is this, that as the subter- 
ranean water level is the result of the absorption of surface 
moisture, whether derived from rain or other meteoric 
changes, so it is affected by the question of surface drainage, 
and is therefore a secondary subject. 
The first principle of artificial drainage is that, which is 
adduced from a consideration of the process adopted in 
nature, by which the rains and surface waters find one 
common level on the surface of the globe ; — this is the 
question of rise and fall in the ground. Let us therefore 
consider a case in point. — Suppose rain to fall on the summit 
of an isolated mountain range, the construction of which 
is uniform, the fall of the ground, from the summit to the 
general level, being the same on all its declivities, the rain 
would naturally find its level by all sides of the range ; and 
the neighbouring strata would all partake of its influence in 
nearly the same degree ; again, suppose this range of hills 
to be composed of an outward barrier of hills, between 
which and the summit, a valley or even a slight depression of 
ground existed ; the case would now become changed — the 
surface waters, which in the former case had found the level 
over all the sides of the range, would now be collected in the 
intermediate valley, and conveyed by these natural channels 
to the first place of exit, if there were such ; or if not would 
form an elevated lake or pool. These two examples, then^ 
show by what means the surface waters are collected by 
nature, and hence we are led to adopt a similar course in 
order to collect the same waters where it is yet needed, and 
thus to modify the irrigation. 
