408 



STATE 130AKD OF AGRICULTUKE. 



UXDEKDRAINING. 



The best possible arraugement of surface drains will not retnove all the water 

 from the road, and in many cases other methods of removing the water must 

 be adopted. The best of all methods will doubtless be found by combining a 

 thorough system of underdrainage with that of turnpiking. In all cases the 

 cross section should have the convex form as shown in Fig. No. 2, so as to jj re- 

 vent as much as possible the absorption of water by the surface of the roadbed 

 projier, which, thongh not joerfectly impervious to Avater under any system of 

 construction, it will, when of this shape, convey the greater portion of the water 

 that falls upon it into the side channels. Even when the underdrain is directly 

 beneath the axis of the road, it is not advisable that the water should reach it 

 by soaking down through the traveled jiortion of the road, which it would ren- 

 der soft and muddy, but it should be, as far as possible conveyed to the side 

 channels, and from thence to the underdrain, thus leaving the track in the 

 center as dry as possible. 



The advocates of underdrainage of roads present three systems which vary in 

 cost and efficiency. Mr. J. Bailey Denton, in the Journal of the Koyal Agri- 

 cultural Society of England for 1857, advocates two two-inch drains beneath 

 the two edges of the road-bed or traveled portion of the road, and consequently 

 about twenty feet apart. The other systems find advocates in Gen. Q. A. Gil- 

 more and in Geo. Waring, and are as follows : 2d, two underdrains, one beneath 

 each ditch formed in turnpiking the road ; 3d, one underdrain beneath the axis 

 or center line of the road. 



