Chap. III. BEOUGHT UP BY WORMS. 169 



was shaded during part of the day by trees. 

 It had been formed at least a century ago by 

 a great accumulation of small and large frag- 

 ments of sandstone, together with some sandy 

 earth, rammed down level. It is probable that 

 it was at first protected by being covered with 

 turf. This terrace, judging from the number 

 of castings on it, was rather unfavourable for 

 the existence of worms, in comparison with 

 the neighbouring fields and an upper terrace. 

 It was indeed surprising that as many worms 

 could live here as were seen ; for on digging 

 a hole in this terrace, the black vegetable 

 mould together with the turf was only four 

 inches in thickness, beneath which lay the 

 level surface of light-coloured sandy soil, with 

 many fragments of sandstone. Before any 

 castings were collected all the previously 

 existing ones were carefully removed. The 

 last day's collection was on October 14th, 

 1871. The castings were then well dried 

 before a fire ; and they weighed exactly 3^ lbs. 

 This would give for an acre of similar land 

 7*56 tons of dry earth annually ejected by 

 worms. 



The second square was marked on un- 



