TRANSACTIONS OF SECTION G. 495 
Elsewhere there are rivers in India, rising in districts;subject to certain heavy 
periodical rainfall, and carrying their waters on to distant plains of very uncertain 
rainfall. Ata small expense channels can sometimes be constructed drawing off 
from the flooded river water sufficient thoroughly to saturate the soil, and render 
it fit to be ploughed up and sown with wheat or barley, which do not require 
frequent watering. The canal soon dries up, and the sown crop must take its 
chance ; but a timely shower of rain may come in to help it, or well irrigation may 
mature the crop. These, which are known in India as inundation canals, are of 
high value. 
Southern India. 
In Southern India there are three great rivers, drawing their supply from the 
line of hills called the Ghats, running parallel to and near the western coast, and 
after a long course discharging into the Bay of Bengal on the east: coast. Against 
the Ghats beats the whole fury of the tropical S.W. monsoon, and these rivers 
for a few months are in high flood. As they approach the sea they spread 
out in the usual deltaic form. Dams have been built across the apex of these 
deltas, from which canals have been drawn, and the flood waters are easily 
diverted over the fields, raising a rice crop of untold value in a land where 
drought and famine are too common. But for the other months of the year these 
rivers contain very little water, and there is now a proposition for supplementing 
them with very large reservoirs, 
A very bold and successful piece of irrigation engineering was carried out a 
few years ago in South India, which deserves notice. A river named the Periyar 
took its rise in the Ghats, and descended to the sea on the west coast, where 
there was no means of utilising the water, and a good deal of money had periodi- 
eally to be spent in controlling its furious floods. A dam has now been built 
across its course, and a tunnel has been made through the mountains, enabling the 
reservoir to be discharged into a system of canals to the east, where there is a vast 
plain much in need of water. 
In the native State of Mysore, in Southern India, there are on the register about 
40,000 irrigation reservoirs (or tanks, as they are called), or about three to every 
four square miles, and the nature of the country is such that hundreds may be 
found in the basin of one river—small tanks in the upper branches and larger ones 
in the lower, as the valley widens out, and these require constant watchful atten- 
tion. From time to time tropical rainstorms sweep over the country, If then even 
a small tank has been neglected, and rats and poreupines have been allowed to 
burrow in the dam, the flood may burst through it, and sweep on and over the dam 
of the next village, lower down. One dam may then burst after another, like a 
pack of cards, and terrible loss occurs. 
In this State of Mysore a very remarkable irrigation reservoir is now under con- 
struction at a place called Mari Kanave. Nature seems here to have formed an ideal 
site for a reservoir, so that it is almost irresistible for the engineer tozdoshis;part, 
even although irrigation is not so badly wanted here as elsewhere. e compara- 
tively narrow neck of a valley containing 2,075 square miles is-being closed by a 
masonry dam 142 feet high. The reservoir thus formed will contain 30,000 
million cubic feet of water, but it is not considered that it will fill more than once 
in thirty years. Nor is there irrigable land requiring so great a volume of water. 
Much less would be suflicient, so such a high dam is not needed ; but the construe- 
tion of a waste weir to prevent the submergence of a lower dam would require such 
heavy excavation through one of the limiting hills that it is cheaper to raise the dam 
and utilise a natural hollow in the hillside for a waste weir. 
Irrigation in Fgypt. 
No lecture on irrigation would,‘be complete without describing what has 
been done in Egypt. You arefgenerally familiar with the shape of that famous 
little country. Egypt proper extends northwards from a point in the Nile 
about 780 miles above Cairo—a long valley, never eight miles wide, sometimes 
not halfa mile. East and west of this lies a country broken into hills and valleys, 
