29
larvæ. When the irrigation water-supply stops, however, a number of pools
remain in this watercourse as in the unbricked ones, and these would also require
constant attention.*
The above descriptions may be taken as fair examples of the methods
employed and the results obtained in all the watercourses of the area of opera-
tions. It will be seen that though various plans were carefully tried, it was not
possible to prevent anopheles larvæ constantly appearing in the watercourses in
large numbers. By continuous efforts it is possible to check the breeding to a
certain extent, and to kill a great many of the larvæ, but if the measures are
stopped for even a week at a time, the condition becomes almost the same as it
would be had no operations at all been carried out.
II.—The Royal Artillery Bazaar Section.
On the 11th of June no breeding places except the irrigation watercourses
were found in this section. On the 17th a few anopheles larvæ were found in a
garden pool in front of the bazaar. This pool was dried out and on the 22nd no
breeding places were found. Search for adults was frequently made during June.
On the 3rd no adult anopheles mosquitoes were found after careful search in many
of the houses, stables, and sheds. On the 16th after nearly an hour's search I
found four adult A. culicifacies in one of the stables. By the 26th the number of
A. culicifacies present in the houses had increased considerably, but they were
still scanty and difficult to catch. This was in marked contrast to other bazaars
in the cantonment where from the beginning of the month adult insects (A.
culicifacies) were present in sufficient numbers to be caught without much difficulty in
many of the houses. No adult A. Rossi were caught in any of the bazaars during
June.
During July a large number of rain-formed breeding places were found from
time to time in this section. These consisted chiefly of large and small pools
formed by holes dug for road-making, building, and other purposes. Along one
roadside there were twenty pools averaging five feet long by two feet deep, which
after a short time swarmed with the larvæ of A. Rossi. Such pools were tempo-
rarily covered with a layer of oil and afterwards filled in with earth. The surface
* Experience has shown that this channel was constructed on an entirely wrong plan. Instead of
simply digging out and bricking the old watercourse as was done in this case, a very narrow channelwith
straight sides should have been built in the bed of the old one, and the fall in this channel should have been
sufficient to prevent any water standing in it when the supply was turned off at the head. If it should
eventually be decided that all irrigation channels in cantonments should be made pucca, the first principle
to be kept in view should be to raise the water at its source from the main irrigation canal to such a height
that it will run swiftly through all parts of the cantonment in very narrow bricked channels with such a fall
that when the water is turned off at the head, all the channels will dry up completely. I am informed that
this plan is quite practicable in Mian Mir and that it would do away with all Persian wheels, syphon bridges,
etc., irrigation being carried on by " flow" instead of by " lift."
The simple bricking of a channel without some such provision as this for ensuring a swift running
stream, is of little avail.