454 Description of the Regulating Dam-Sluices. [Oct. 



is but rarely found in veins, and never is, I believe, the sole substance 

 that fills a vein. My second reason is, that he describes it as passing 

 into the limestone with which it is connected. Now, it is usually in- 

 ferred, that rocks in juxta-position, which approximate and gradually 

 pass into each other, are contemporaneous, or at least next in succession 

 to each other. The passage of one into the other at least proves, that the 

 one, if not semi-fluid, was loose, earthy, and unconsolidated, so as to ad- 

 mit of being penetrated by the other, at the time of their junction. 



IV — Description of the Regulating Dam-Sluices of the Doab Canal. 



To provide a clear and open water-way during floods, unimpeded 

 by the superstructure, which is generally attendant on sluice gates, and 

 to facilitate their removal on sudden freshes, the following construc- 

 tion has been adopted at the dams over the large mountain tor- 

 rents that cross the Doab canal in the country north of Saharunpur. 

 Although merely a modification of the old self-regulating gate, 

 it may be perhaps worth noticing, as I am not aware that an arrange- 

 ment similar in detail has either been put in practice before in works 

 of this nature, or that gates depending on lower pivots for their 

 movements, have ever been alluded to in any books treating of canal 

 works. 



It may be necessary to mention, that the mountain torrents which 

 cross the lines of the Doab canal, in their northern extremities, 

 only flow during the rainy months, when continued falls of rain 

 in the lower mountain range, and on the belt of forest that skirts them 

 to the south, give rise to very sudden and rapid drainage, which being 

 effected on the line of these rivers, or as they are provincially termed 

 rows, cross the canal at right angles, and pass off" by a series of sluice 

 openings, fixed in masonry dams across their channels. On these 

 occasions the volume of water is not more to be guarded against 

 than the quantity of floating logs, large forest trees, roots, grass, &c. 

 that the water collects in its course, for all of which a passage is as 

 absolutely necessary as for the water itself. As the canal supply of 

 water depends entirely on these masonry dams, and the facility of 

 regulating the sluices in them, so that they may remain closed and 

 be opened upon the occurrence of sudden freshes, is of absolute ne- 

 cessity, the main point, to be^ attended to, is to provide openings 

 sufficiently large for the escape of the greatest quantity of water 

 that the channel will carry, yet of such a size that the opening and 

 shutting of the whole line can be effected in the shortest possible 



