THIRD ANNUAL YEAR BOOK — PART I. 



31 



loosens the soil. One hundred volumes of water make, when frozen, 109 

 volumes of ice. When the warm spring weather comes, this ice melts, 

 and, as there is no place for the water to go, the ruts in the springy 

 soil become deeper and deeper until wagons often sink to their hubs and 

 horses flounder laboriously through the resulting slough. (Fig. 9.) The 



Pig. 9.— Poorly drained eartli road. 



remedy, therefore, is to get rid of the water in the foundation of the 

 road, and get rid of it before it has time to soften the substructure or 

 freeze. For this purpose it is advisable to construct horizontal drains 

 under the roadway, which should empty into the open drains or the 

 natural water courses at frequent intervals. (Fig. 10.) If the road sur- 



FiG 10 — Cross sectio of underdrained road. If \ower outlets can be secured subdrains 

 may be placed as at a and b, or direct\y under side ditches. 



face is composed of retentive soils, such as fine clay, there should be two 

 or three drains; but if the soil is open or pervious, and if two drains 

 are considered too expensive, one drain in the center of the traveled 

 way (Fig. 11) will often be found to suffice. 



DEPTH AND FALL OF SUBDRAINS.— The depth to which drains 

 should be laid will depend upon the character of the soil as well as the 

 depth of the frost line. These drains can be placed parallel with the sur- 



