( 8 ) 



of the walls to the bed of the river. Likewise on the up- 

 stream face of these weir walls is a bund of stones, of 

 greater or lesser extent, sloping down to the bed of the river. 

 XIII. These irrigation weirs are of different forms, 

 but all arrest the passage of fish, 



Irrigation weirs, under-slu ices ., x .-, ,. -, 



either narrow or wide; no fish some temporarily, others entirely; 

 able to ascend through the andas a consequence those migrating 



former. . 



down-stream often pass into the 



irrigation canals. These weirs have openings of varying 

 sizes termed " under-sluicea," constructed for the purpose of 

 permitting the surplus water passing through the body of the 

 weir, and on a level with the lowest bed of the river ; when 

 rushing through with great velocity, it was expected large 

 quantities of silt would be carried with it, keeping the 

 general bed of the river washed out to its proper level. 

 These under-sluices or complete gaps through the weirs are 

 of different widths, and may be classed under two divisions : 

 first, the long narrow ones in Madras, the North- Western 

 Provinces, and the Panjab; and, secondly, the wide ones in use 

 at Cuttack, Midnapur, and on the Sone River. These under- 

 sluices are kept closed, except when there is an excess of 

 water, as during the monsoon months : those of the Madras 

 pattern are from six to nine feet in width and several yards in 

 length; they close by means of boards pushed down 

 vertically into large wooden grooves, and these boards 

 can be elevated, when it is desired to do so, by means 

 of a capstan and jrindlass. As these narrow under-sluices 

 are of many feet in length, there are generally two sets 

 of grooves, one at each end, so that either can be made use 

 of. These narrow under-sluices carry such a rush of 

 water through them that no Indian fish can ascend up 

 when they are open. I thought this had been clearly esta- 

 blished, but as I see this belief again advanced, I must here 

 digress in order to explain that such never occurs. Fish, 

 which are attempting to pass weirs in the course of their 

 ascent up rivers, are chiefly those who are in a breeding con- 

 dition, and are trying to reach their natural spawning grounds. 

 Thus, when near the sea, the shad or hilsa is the most valu- 

 able sort which becomes stopped by weirs without practicable 

 passes, so they are unable to reach the only localities wherein 

 their spawn or ova could come to maturity if deposited ; they 

 consequently have to drop it in the water below these weirs, 

 and here it cannot be fertilised, but inevitably perishes. The 

 same occurs with some of the large carps in the more north- 

 ern rivers (as of the North- Western Provinces and the Panjab) 



