EARTH-WORMS AND THEIR WORKS. 



297 



The estimates of the amount of mold brought up by the worms, 

 based on actual weighings and measurements of the castings at par- 

 ticular spots, give results ranging from 7'56 to 1S-12 tons per acre in 

 one year, and a volume sufficient to make when spread out a layer of 

 soil of from one to more than two inches thick in ten years. 



" Archreologists," says Mr. Darwin, "are probably not aware how 

 much they owe to worms for the preservation of many ancient Objects. 

 Coins, gold ornaments, stone implements, etc., if dropped on the sur- 

 face of the ground, will infallibly be buried by the eastings of worms 

 in a few years, and will thus be safely preserved until the land at 

 some future time is turned up." The remains of ancient buildings 

 seem also to have been buried effectively, in large part, through the 

 action of worms. An example of this kind is furnished at Abinger, 

 Surrey, where the remains of an ancient Roman villa were discovered 

 in 1877. The cut (Fig. 6) represents the appearance presented by the 

 buried wall and the ground ai"ound it at a point where one of the 

 trenches was dug. The mold here was from eleven to sixteen inches 

 thick over the tesselated floor, G, and from thirteen to fifteen inches 

 thick over the broken summit of the wall, W. No signs of worms 

 appeared on the trodden-down earth over the tesserce when they were 

 first cleared, but many signs of fresh worm-action were seen on the 

 next day, and for the next seven weeks these signs were very abundant. 

 Numerous burrows were also found in the course of the digging, and 

 worms were brought up from a considerable depth. Three years after- 

 ward the worms were still at work, burrowing in the concrete floor and 

 the mortar of the walls, as they had probably been doing ever since 



^m 



Mould, 9 inches 

 thick. 



Mass 1 f rubbish 

 27 Inches thick, 

 overlying i 

 pile >,f charred 



Tesscr.T. n 

 on concrete. 



Fig. 7.-Section mTHiN a Boom in the Basilica at Silchester. Scale -fa. 



the concrete had become decayed enough to allow them to penetrate 

 it; and even before that period they probably lived under the floor, 

 making burrows which, collapsing from time to time, helped make the 

 walls and floor sink. 



