Leith Hill Place, during 369 days, calculated to yield annually per acre 7.56 tons.
(4.) Castings collected from a square yard on Leith Hill Common during 367 days, calculated to yield annually per acre 16.1 tons.
The thickness of the layer of mould, which castings ejected during a year would form if uniformly spread out.—As we know from the two last cases in the above summary, the weight of the dried castings ejected by worms during a year on a square yard of surface, I wished to learn how thick a layer of ordinary mould this amount would form if spread uniformly over a square yard. The dry castings were therefore broken into small particles, and whilst being placed in a measure were well shaken and pressed down. Those collected on the Terrace amounted to 124.77 cubic inches; and this amount, if spread out over a square yard, would make a layer .09612 inch in thickness. Those collected on the Common amounted to 197.56 cubic inches, and would make a similar layer .1524 inch in thickness.
These thicknesses must, however, be corrected, for the triturated castings, after being well shaken down and pressed, did not make
