On Trunk Drainage. 



369 



only with regard to tlie passage over, having low and narrow arches 

 and uselessly large piers; and lastly, though not the least cause 

 of damage on many streams, are the mills. In many instances 

 a mill affects the drainage of much land, sometimes hundreds of 

 acres above it, and does yearly more damage to such lands by 

 pounding the water than its annual rent bears any comparison to. 



I believe there can be found, with few exceptions, a sufficient 

 fall in the course of all rivers and brooks to carry off superfluous 

 water^ and to drain or give good outfall for the under-drainage of 

 the adjoining lands. 



In order to obtain the advantage of that outfall, the water of the 

 small brooks should not be carried off by watercourses of a less 

 depth than 4 feet, having a regular incline at the bottom, and in 

 as straight a line as the nature of the course will admit of, the 

 curves being- of a radius large enough to allow the water to run 

 easily round them. The size and depth of the watercourse must 

 of course depend on the quantity of water it is required to carry 

 off, and the nature of the land it has to pass through. 



To carry off the water from larger streams all the obstructions 

 in their bed and sides require to be removed, the turns straight- 

 ened, the channels made of as regular a width and depth as prac- 

 ticable, and the bridges, where not large enough, altered, or 

 arches added to them. 



Ample outfall might be obtained on some rivers by abolishing 

 some of the mills or other impediments of like nature, and scour- 

 ing out and deepening their present channels, and on other 

 streams that are very winding by merely straightening their 

 course, which in streams from about 15 to 25 feet wide would be 

 of comparatively small expense. 



By obtaining the best fall for the water of the rivers an oppor- 

 tunity would be opened for irrigating the land now damaged by 

 their overflow, particularly where a mill could be done away with : 

 and now the application of steam power is so general, there re- 

 mains no necessity for keeping up many of the watermills, which 

 axe not unusually situated too far from market to be able to enter 

 into trade against the competition of mills close to markets or 

 railway stations, and inconveniently and too thickly placed as 

 regards grinding the corn of the district ; the water required for 

 a mill, setting aside the damage it might do by its present use, 

 would often, if applied to the irrigation of the land, make a much 

 greater return. 



The improvements I have suggested may be effected to a con- 

 siderable extent on large or compact estates, and in small streams 

 much improvement, even in short distances, might frequently be 

 made at a trifling expense ; but there exist at present too many 

 legal difficulties in the way of accomplishing them where rivers 



