166 WEIGHT OF EAETH Chap. III. 



particles were thus often lost. The lady also 

 occasionally left home for a week or two^ and 

 at such times the castings must have suffered 

 still greater loss from exposure to the weather. 

 These losses were, however, compensated to 

 some extent by the collections having been 

 made on one of the squares for four days, and 

 on the other square for two days more than 

 the year. 



A space was selected (October 9th, 1870) 

 on a broad, grass-covered terrace, w^hich had 

 been mowed and swept during many years. 

 It faced the south, but was shaded during 

 part of the day by trees. It had been 

 formed at least a century ago by a great 

 accumulation of smal 1 and large fragments 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 w^orms, 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 



