quantity would cost £1,360,000, and therefore a 3 in. storage as above
would require an outlay of, say, £15,000,000 sterling; and it will be
seen that 3 in. is by no means too great a rainfall to allow for, as in
July of 1875, according to Mr. Symons, at Cirencester, 3.11 in. fell
within twenty-four hours. Supposing serious attention were to be given to
such a scheme, there would, without doubt, be very great difficulty in
finding suitable situations, from an engineering and land owner's point
of view, for the requisite dams and reservoir areas.

In Great Britain and many European countries rain gauges have been
established at a greater or less number of stations for many years past,
and data thereby afforded for estimating approximately the rainfall of
any given district or catchment basin. The term "watershed" is one which
it appears to me is frequently misapplied; as I understand it, watershed
is equivalent to what in America is termed the "divide," and means the
boundary of the catchment area or basin of any given stream, although I
believe it is frequently made use of as meaning the catchment area
itself. When saying that the rain gauges already established in most of
the older civilized countries afford data for an approximate estimate
only, it is meant that an increase in the number of points at which
observations are made is necessary, previous to the design of a reservoir
dam on the catchment area above, the waters of which are proposed to be
impounded, and should be continuous for a series of five or six years,
and these must be compared with the observations made with the old
established rain gauges of the adjacent district, say for a period of
twenty years previously, and modified accordingly. This is absolutely
necessary before an accurate estimate of the average and maximum and
minimum rainfall can be arrived at, as the rainfall of each square mile
of gathering ground may vary the amount being affected by the altitude
and the aspect as regards the rainy quarter.