Uequhaet. — On the Work of Earth-ivorms. 121 



The test in the lower land (mentioned above), a black 

 arenaceous loam, was submitted to rather severe conditions — 

 that is, the coarse wood-ashes and broken brick were spread 

 over a thick sward of cocksfoot grass, from which stock is always 

 excluded. Last September, when the strong grass was shaved 

 off close to the surface and a trench opened up, the section in 

 the vertical sides of the walls showed that all the debris was 

 buried beneath an average depth of rather more than f ths of an 

 inch of mould ; the layer forms a horizontal line |ths of an inch in 

 thickness, but most of the debris is more or less entangled 

 amongst the roots, consequently does not represent a compact 

 and well-defined line ; some of the fragments of brick, about 

 li inches square, weighing over loz., have sunk about li inches 

 beneath the surface. This irregularity is to be attributed to the 

 fragments having remained entangled amongst the grass for a 

 more or less length of time, consequently buried at various 

 intervals. It will be observed that there is a difference of about 

 half an inch between the increase to the superficial layer in the 

 upper and lower lands, which is easily accounted for : it was an 

 oversight on my part that, when the debris was scattered over 

 the latter, a portion of the grass was not skimmed off; this 

 would have given the worms a fair chance of more rapidly 

 burying the material thrown over it ; however, this error will 

 be remedied before next winter. 



The larger of the two stones mentioned in the former paper, 

 which was laid on the turf in May, 1876, when raised on the 

 15th October, 1883, left a cast 2 inches in depth; when again 

 examined on the 26th September, 1886, it was firmly embedded, 

 and required some force to raise it ; the most protuberant point 

 was 3 inches beneath the level of the surface, the raised margins 

 being removed ; the flatter portion had sunk 2 j-% inches ; worm 

 burrows were numerous beneath. The smaller stone, which 

 was placed near the former in September, 1882, sank in thir- 

 teen mouths 1 inch ; on the 26th September of the present year 

 it had attained a depth of 2 inches below the general level of 

 the ground ; its convex margins were partially covered with 

 worm castings and grass ; it will, if left undisturbed, soon 

 become entirely buried beneath the surface. It is w^ell, perhaps, 

 to bear in mind that under favourable conditions, through the 

 agency of earth-worms, it is possible for a stone 6^ inches long, 

 3^ inches broad, and 3f inches in thickness, to disappear below 

 the surface of the ground in about seven or eight years. 



The experimental stones laid on the turf on October 15th, 

 1883, when recently examined gave the following results : — 



No. 1, triangular block of trachyte, 6 inches high, when 

 raised left an impression 6 inches long, 4^% inches 

 wide, depth below general level of the ground 1^% 

 inches. 



