168 WEIGHT OF EAETH CHAP. III. 



during a year all the castings thrown up on 

 two separate square yards, near Leith Hill 

 Place, in Surrey. The amount collected was, 

 however, somewhat less than that originally 

 ejected by the worms ; for, as I have repeatedly 

 observed, a good deal of the finest earth is 

 washed away, whenever castings are thrown up 

 during or shortly before heavy rain. Small 

 portions also adhered to the surrounding 

 blades of grass, and it required too much 

 time to detach every one of them. On 

 sandy soil, as in the present instance, castings 

 are liable to crumble after dry weather, and 

 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) for 

 one of the squares on a broad, grass-covered 

 terrace, which had been mowed and swept 

 during many years. It faced the south, but 



