Chap. I.J 



COILVL AVELLS. 



21 



in some places, where the soil is hght, the smface of 

 the ground is a hollow arch, so that it resounds as if a 

 horse's weight were sufficient to crush it inwards. This 

 is strikingly perceptible in the vicinity of the remark- 

 able well at Potoor^, on the west side of the road lead- 

 ing from Jaffiia to Point Pedi^o, where the surface of 

 the surrounding country is only about fifteen feet above 

 the sea-level. The well, however, is upwards of 140 

 feet in depth ; the water fr-esh at the surface, bracldsh 

 lower down, and intensely salt below. According to 

 the universal belief of the inhabitants, it is an under- 

 ground pool, which commumcates with the sea by a 

 subterranean channel bubbhng out on the shore near 

 Kangesentorre, about seven miles to the north-west. 



A similar subterranean stream is said to conduct to 

 the sea from another singular well near Tillipalli, in 

 sinkuig which the workmen, at the depth of fourteen feet, 

 came to the ubiquitous coral, the crust of which gave 

 way, and showed a cavern below containing the water 

 they were in search of, with a depth of more than thirty- 

 three feet. It is remarkable that the well at TilhpaUi 

 preserves its depth at all seasons alike, uninfluenced by 

 rains or drought ; and a steam-engine erected at Potoor, 

 mth the intention of irrigating the surrounding lands, 

 failed to lower it in any perceptible degree. 



Other wells, especiaUy some near the coast, maintain 

 thek level with such uniformity as to be inexliaustible at 

 any season, even after a succession of years of di^ought — 

 a fact from which it may fairly be inferred that tlieir 

 supply is chiefly derived by percolation from the sea.''^ 



^ For the particulars of this singiilar 

 well, see Vol. II. Pt. ix. ch. vi. p. 536. 



~ Daraat:n, in his admirable account 

 of the coral fonnations of the Pacific 

 and Indian oceans, has propounded a 

 theor\r as to the abundance of fresh 

 water in the atolls and islands on 

 coral reefs, furnished by wells which 

 ebb and flow -w-ith the tides. Assum- 

 ing it to be impossible to separate 



salt from sea water by filtration, he 

 suggests that the porous coral rock 

 being pemieated b}' salt water, tlie 

 rain which fiills on the siu-face must 

 sink to the leA'el of the si r rounding 

 sea, "and must accumulate there, 

 displacing an equal bulk of sea water 

 — and as the portion of the latter in 

 the lower part of the gi-eat sponge- 

 like mass rises and falls with the 



