district in Great Britain, viz., Cumberland, averages not more than 70
in. per annum.

The rainfall in Bombay is from 80 in. to 100 in. per annum, and
throughout India may be taken as from 50 in. to 130 in., varying, as is
the general rule, in direct ratio with the altitude, and limited to a few
weeks in the year. Notwithstanding this, there still exist in the Madras
Presidency a not inconsiderable number of ancient bunds which serve their
intended purpose at the present day as well as ever. Slight mistakes did
occasionally occur, as they ever will till no more dams are wanted, as is
proved by the remains of some works in Ceylon, where the failure was
evidently due to error, possibly due to the instruments being out of
adjustment, as their base is at a higher level than the bed of the stream
at the point where water from the latter was to be diverted to afford the
supply.

Among the most remarkable of these ancient works is the Horra-Bera tank,
the bund of which is between three and four miles in length and from 50
to 70 ft. in height, and although now in ruins would formerly impound a
reservoir lake of from eight to ten miles long and three to four miles
broad. There is also the Kala-Weva tank, with a bund of twelve miles in
length, which would, if perfect, create a lake of forty miles in
circumference. Both of these ruined works are situated in Ceylon. The
third embankment of a similar character is that of the Cummum tank,
situated in the Madras Presidency, and which, though ranking among the
earliest works of Hindoo history, is still in such a condition as to
fulfill its original intention. The area of the reservoir is about
fifteen square miles, the dam about 102 ft. high, with a breadth at the
crest of 76 ft., and of the section shown in the diagram.