1919.] The Sixth Indian Science Congress. ecix 
rivers; their distribution in relation to the nature of the water; their 
rtance as providing food and shelter to mosquito larve 
Contamination of the river with sullage takes place by the inflow of 
e City’s a into the river; bu 
alari jes 0 
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This is ies. At the process of self-purification of sor streams as a result of 
various factors, physical as well as biological ; rease of aquatic veget- 
_ growth as a result of the onuealnahians : : once ion of larvicidal 
oo 
study is made of the comparative prevalence of the different spe- 
cies of anophilines in nase pp to the variation in dissolved oes Rev patra in 
waters ; the r d fall of the different — as shown by a graph. 
“The ilamentanilicians in i oo to disease; suggested setbosibn of control ; 
control. of a — —— and algal growths. Experiments on the 
me In s 
chilus, Ba ee and Nuria A discussion on the usefulness of aquatic 
birds like ducks and g 
Hydrocyanic acid “i as an insecticide.—By W. GLEN 
Liston andS8S. N. Gor 
The officers of the Parel Laboratory have for some years been engaged 
in the study of a variety s mepctiener. with the re ape a a num- 
ber of useful means for destroying insects have n sed each of 
which is applicable for use under s aegiat circumstances. Of ‘lly gies 
insecticides kerosene oil or hydrocarbon emulsion have been very 
effective “Canain ham’s method of killing fleas by laying aaa anc 
sun 
these ides car s 
RY found to rm of little practical use while Hydrocyanic Acid Gas, used 
n the limit of temperature found in Bombay, has been proved to 
be effective i in killing the eggs, larval, = and imago stages of insects. 
Much ingenuity has been expended in devising methods for applying this 
gas to practical purposes and while ee yet remains to be oO per- 
fect the er gcmipn ‘considerable Progress ress has been made. 
One ps in the sighs gh of these methods 
has been the use a solutions . pot assium cy and sulphuric acid 
for generating the gas. Experience has shown that te most convenient 
concentration of these solutions for use is 33°3% strength of each in i ae 
All that is required to effect the convenient generation of the g 
pour the two solutions into separate vessels and to allow the Taide t 
in 
mix slowly open dish placed within th solutions are 
passed into the nay Magneto is bed ted through tubing and they 
allowed to run into th ame rate bei ‘ . The 
two tubes pv ss the ‘solutions into the open immediately 
over the flat dish fixed in the The whole ‘appaiseas can be fixed to 
the r of a room as is iow ar he plan 
An arrangement of this kind is eminently suitable for small rooms of 
from 100 to 500 cubic feet capacity but a ge rooms “vty < be 
used more elaborate arrangements for co e gas thro 
room are required. The arrangements satiate for a a room for de- 
lousing the kit of soldiers is shown in the next plans. 
The quantity of chemicals required for one hundred - cubic » Sook: “ 
are half eac 
sulphuric acid. It is important to note that the potassim ease 
pure. Under satisfactory conditions where rel is very little i of gas 
from the room and the room is empty, half an ounce 
by when 
of potassium cyanide mixed in this way with half an ounce of ana et 
