438 Of the Bogs in Ireland. 



proper lines of direction for one or more main drains pass- 

 ing through it, to give vent to the waters which it contains, 

 and for catch-water drains laid out along its edges, to inter- 

 cept the springs and streams which flow into it from the ad- 

 joining lands. 



" 5th. — In laying down the situation of the main drains, 

 the engineers are to consider, not merely the general de- 

 clination of the bog towards the rivers or such or other na- 

 tural outlets as may best answer for their drainage, but to 

 keep in view the further object, where practicable, of con- 

 verting these main drains, either immediately or ultimately, 

 into channels of navigation, for the conveyance of the fu- 

 ture productions of the bog, and of providing for the con- 

 nexion of those navigable drains, where convenient, wich 

 the great lines of navigation already subsisting : where this 

 is not possible, they are to consider how these different 

 drains may be united to other canals, which may be formed 

 hereafter. In laying down the situation of any navigable 

 drain, the engineers are to attend to the situation of such 

 manures as may be most suitable for the bog. 



" 6th. — Where the main drains are likely to be used as 

 i canals, they are not, in any instance, to be less than 14 feet 

 broad at bottom, and rive feet deep from the water surface. 

 The breadth and depth of other main drains, and of the 

 catch-water drains, must be proportioned to the quantity of 

 water which they are to discharge. 



" 7th. — As there are no districts which are more liable 

 to the inconvenience of a total want of water in dry sum- 

 mers, than level tracts of marshy ground, when once their 

 drainage is effected, care must be taken in laying down the 

 direction of the main drains, to allow them, where prac- 

 ticable, to be occasionally dammed up, so as to raise the 

 water within two feet of the surface, for the purpose of 



ftromoting vegetation ; and that the catch-water drains, in 

 ike manner, should supply water on the surface, for the 

 use of cattle, or for the purpose of irrigation, where the 

 mode of improvement shall be deemed advisable ; and in 

 situations where a sufficient supply cannot be procured by 

 these means, the engineers are to consider where reservoirs 

 may be most advantageously constructed, to be supplied, 

 in time of Hood, from the caich-water drains or rivulets in 

 the vicinity of the boos. 



" 8th. — Where locks may be necessary, the dimensions 

 which the commissioners recommend are, feet, in- 



Length 70 



Breadth 7 3 



Depth over the fill of the gates ..40 



(i 9th. — Ib 



