EXCAVATION OF MARL IN HILLY LANDS. 287 



Suppose the marl to " crop out," or otherwise to come near to 

 the surface near the foot of a high hill-side (as at c), a ravine and 

 stream being at the bottom (s), and table-land at the top of the 

 hill-side, over which the marl is to be carted to the fields, after 

 rising the hill-side by a graduated road. These are common natural 

 features of marl localities, in hilly lands (and of class II). The 

 out-crop, or natural exposure of the marl (c) is on a convex curve 

 of the hill-side. The first operation is to clear off the little over- 

 lay of earth, -from above the out-crop (o), so as to uncover a suffi- 

 cient space for digging and carting (o, c.) This space should be 

 (if practicable), 15 feet across, of horizontal width, to permit sin- 

 gle-carts to turn upon ; and as long (with the course of the stream) 

 as the ground may permit, say 30 feet or more. This small amount 

 of overlying earth (o) is easily disposed of, by being thrown into 

 the ravine, or across the stream. The uncovering reaches to the 

 top of t^ie marl stratum, which is supposed 12 feet thick ; of which, 

 8 feet are above and 4 below the level of the stream. A road is 

 next laid off, graduated to best advantage, and constructed, de- 

 scending from the upper table land to the uncovered marl, the lower 

 end of the road being on a level about 1 foot higher than the 

 stream, and of course 5 feet above the bottom (m, m), of the marl 

 fit for use. (The lowest part is usually too poor, and sometimes 

 too much affected by water, to be worth being removed.) If springs 

 ooze out over the top of the marl, a little trench (y) of about 4 

 inches wide and as many deep, must be made along the back line 

 of the uncovering, to cut off and convey away the spring water. 

 The uncovered and drained marl (c, ,) is then dug and carted out ; 

 the work being so conducted as to level the surface, and enable the 

 carts as soon as the surface is enough lowered, to pass over, turn 

 about, and be loaded upon the marl. When the whole space has 

 been dug down to the level of the lower end of the road (a, ,) 

 then a perpendicular pit should be dug at the end of the area 

 farthest from the descending road, and across its whole width. 

 This pit (p p) will be 15 feet long, about 6 to 9 wide, as may 

 be most convenient, and 5 deep when finished to the bottom. The 

 carts turn on the area (a, t,) and are loaded at the edge of this 

 pit. When finished, another similar pit is dug alongside; and 

 others in succession, until the whole area of the first uncovered 

 marl has been so pitted out. The overlay (d) is then dug and 

 thrown off from the next range or section of marl (/), so as to 

 uncover another width of 15 feet. The removed earth here (d), 

 where highest, might have been more than 10 feet thick. But the 

 space excavated for the first range of marl (cjp) has more than 

 room enough to receive all this earth. 



The carts now have to be supplied from the second range of 

 marl (/). As this is throughout of the full thickness of the bed, 



