276 MASSACHUSETTS AGRICULTURE. 



vals to relieve the hillside ditches. All the ditches named 

 should communicate as quickly as possible with natural water- 

 courses, and special care be taken in their construction, that 

 they may not be washed or overtaxed in a freshet. 



In general, no work upon a road pays better than that which 

 tends to secure a perfect system of drainage, keeping the water 

 level three feet below the surface of the road. And it may be 

 observed that the vicinity of the road should be kept clear of 

 trees and bushes, as they obstruct the sun and wind and pre- 

 vent evaporation. Hence shade-trees, set along the margins for 

 beauty and comfort to the traveller, should not be placed too 

 frequently, and only in dry and exposed places. 



Bridges and Culverts. 



Upon this subject abundant instruction has been published in 

 a multitude of works, both in a scientific and in a popular way, 

 and we will briefly state a few general principles. 



The leading point in these structures is to make them perma- 

 nent. Ample provision for the severest freshets — like the one 

 last October — must be made by a careful and exhaustive study 

 of each locality. Above all, secure for these costly structures 

 foundations that cannot possibly settle beneath any pressure 

 they may have to bear, and which cannot be undermined. The 

 safest way is to place them very deep, and heavily timber the 

 bottom if it is at all yielding or treacherous in its nature. 

 Quicksand, the most fickle of all, will support the heaviest of 

 structures if it can be confined. Piling, topped with a platform 

 of timbers alternately crossing, or the tops embedded in a thick 

 layer of concrete, has never failed the engineer when the work 

 has been skilfully done, and properly protected by rip-rap or 

 otherwise. 



In cases where a soft material lies upon rock, not many feet 

 below, the excavation must extend to the rock-bed, and this is 

 the best kind of a foundation. 



Special attention should be given to the lower ends of cul- 

 verts to prevent their undermining. This may be effectually 

 done, if necessary, by transverse walls of masonry, or rows of 

 sheet piling, placed beneath the bed of the stream, and the 

 intervals filled with large stones. 



A great thing is to give an abundance of water way. By 



