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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 (ioth 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. 



