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strong sun. The ground was cracked, but, as far as I could find, 
a tunnel nowhere had connection with the outside world by a crack, 
still they may have in a few instances allowed the escape of some 
of the poisonous fumes which, however, move but slowly upwards. 
The holes were difficult to find : several appear to have been aban- 
doned ones, and the two ends could not always be identified. 
However the experiments were highly successful. Thus in the 
first hole poisoned on Monday afternoon (joth February) and 
opened about 8 A. M. next morning ten dead rats were found. 
In others varying numbers 8 to io, including nests of young ones, 
were turned out. In all cases the rats were quite dead, not 
partially suffocated. How long they survive I cannot say, but 
this is not of practical interest. In no instance do they appear 
to have made an effort to get out of the tunnels, though some were 
intentionally closed with very little clay. The young rats were 
found in various parts of the tunnel ; the older ones in its deepest 
part. The relative number of full-grown rats was small owing to 
the time of day at which the holes were poisoned. 
The physical conformation of paddy fields renders the applica- 
tion of carbon bisulphide very feasible, which in or about houses, or 
in grain fields at home, for example, where the holes are scattered, 
would be difficult. In the paddy fields the tunnels are confined 
to the batas, and mostly to the place where three or four batas 
meet. 
I do not know if the bata running in one direction, that of the 
slope of the field, are usually higher and thicker than those running 
at right angles, but in the field in which the experiments were 
carried out, the bigger batas run from East to West the direction 
of the slope, while those running North and South were mostly 
smaller and lower and contained comparatively few tunnels. 
The tunnels vary up to nine feet in length, they run longitudinally 
in the direction of the batas, and seldom as low as the level of the 
paddy area. In most cases there is an offshoot in which the nests 
appear to be made. This is often below the level of the paddy 
area, but many have been formed after the surface water was 
taken off. Each tunnel has two openings. One by which the 
animal usually enters and leaves, this is the one through which 
the earth taken out of the tunnel was carried; the other is much 
smaller, sometimes difficult to find, and, with European rats, at any 
rate, used as an entrance and exit in emergencies. Both these 
holes must be closed when carbon bisulphide is applied. I believe 
it is sufficient to put saturated cotton wool in the larger one, 
I think the carbon bisulphide put in at one end will slowly diffuse 
from the middle of the tunnel up to the other end. 
The depredations were reported too late in the paddy season for 
any definite action other than experiment to be undertaken. With 
the view of starting a definite plan of campaign early next paddy 
season I may be permitted to review the means at our disposal to 
exterminate rats. 
