tensive drainage produces on
the main water-courses of districts, is that of increasing the
height of their rise at flood times, and rendering the flow and
subsidence more rapid than before. I have repeatedly heard the
River Tweed adduced as a striking instance of this fact, and that
the change has taken place within the observation of the present
generation."

_Mr. Maccaw._--"It has been observed that, after extensive
surface-drainage on the sheepwalks in the higher parts of the
country, and when the lower lands were enclosed by ditches, and
partially drained for the purposes of cultivation, all rivers
flowing therefrom, rise more rapidly after heavy rains or falls of
snow, and discharge their surplus waters more quickly, than under
former circumstances."

_Mr. Beattie._--"It renders them more speedily flooded, and to a
greater height, and they fall sooner. Rivers are lower in Summer
and higher in Winter."

_Mr. Nielson._--"The immediate effect of the drainage of higher
lands has often been to inundate the lower levels."

In a prize essay of John Algernon Clarke, speaking of the effect of
drainage along the course of the River Nene, in England, he says:

"The upland farms are delivering their drain-water in much larger
quantities, and more immediately after the downfall, than formerly,
and swelling to the depth of three to six feet over the 20,000
acres of open ground, which form one vast reservoir for it above
and below Peterborough. The Nene used to overflow its banks, to the
extreme height, about the third day after rain: the floods now
reach the same height in about half that time. Twelve hours' rain
will generally cause an overflow of the land, which all lies
unembanked from the stream; and where it is already saturated,
this takes place in six or even in two hours. Such a quick rise
will cause one body of flood-water to extend for forty or fifty
miles in succession, with a width varying from a quarter of a mile
to a mile; but it stays sometimes for six weeks, or even two
months, upon the ground. And those floods come down with an
alarming power and velocity--bridges which have stood for a century
are washed away, and districts where floods were previously unknown
have became liable to their sudden periodical inundations. The land