2-2 



PHYSICAL GEOGRAPHY. 



[PART I. 



A general idea of the aspect of Ceylon will be formed 

 from what has here been described. Nearly four parts 

 of the island are undulating plains, slightly diversified 



tides, so will the fresh water near the 

 surface." Naturalist's Journal, ch. 

 xx. But subsequent experiments 

 have demonstrated that the idea of 

 separating the salt by nitration is not 

 altogether imaginary, as Darwin seems 

 to have then supposed, and Mr. WITT, 

 in a remarkable paper On a peculiar 

 power possessed by Porous Media of re- 

 moving matters from solution in water, 

 has since succeeded in showing that 

 "water containing considerable quan- 

 tities of saline matter in solution may, 

 by fnerely percolating through great 

 masses of porous strata during long 

 periods, be gradually deprived of its 

 salts to such an extent as probably to 

 render even sea-water fresh." Philos. 

 Mag., 1856. Divesting the subject 

 therefore of this difficulty, other 

 doubts would appear to present 

 themselves as to the applicability of 

 Darwin's theory to coral formations 

 in general. For instance, it might 

 be suggested that rain falling on a 

 substance already saturated Avith 

 moisture, would flow off instead of 

 sinking into it ; and that being of 

 less specific gravity than salt water, 

 it would fail to "displace an equal 

 bulk " of the latter. There are some 

 extraordinary but well attested state- 

 ments of a thin layer of fresh water 

 having been found on the surface of 

 the sea, after heavy rains in the Bay 

 of Bengal. (Joum. Asiat. Soc. Seng. 

 vol. v. p. 239.) Besides, I fancy that 

 in the majority of atolls and coral 

 islands the quantity of rain which 

 areas so small are calculated to inter- 

 ceptwould be insufficient of itself to ac- 

 count for the extraordinary abundance 

 of fresh water drawn daily from the 

 wells. For instance, the superficial 

 extent of each of the Laccadives is 

 but two or three square miles, the 

 surface soil resting on a crust of coral, 

 beneath which is a stratum of sand ; 

 and yet on reaching the latter, fresh 

 water flows in such profusion, that 

 wells and large tanks for soaking 



coco-nut fibre are formed in any place 

 by merely "breaking through the crust 

 and taking out the sand." Madras 

 Journal, vol. xiv. It is curious that 

 the abundant supply of water in these 

 wells should have attracted the at- 

 tention of the early navigators, and 

 Cosmas Indicopleustes, writing in the 

 sixth century, speaks of the numerous 

 small islands off the coast of Tapro- 

 bane, with abundance of fresh water 

 and coco-nut palms, although these 

 islands rest on a bed of sand. (Cos- 

 mas Ind. ed. Thevenot, vol. i. p. 3, 

 20.) It is remarkable that in the 

 little island of Ramisseram, one of 

 the chain which connects Adam's 

 Bridge with the Indian continent, 

 fresh water is found freely on sinking 

 for it in the sand. But this is not 

 the case in the adjacent island of Ma- 

 naar, which, being more solid, partici- 

 pates in the geologic character of the 

 interior of Ceylon. The fresh water 

 in the Laccadive wells always fluc- 

 tuates with the rise and fall of the 

 tides. In some rare instances, as on 

 the little island of Bitra, which is the 

 smallest inhabited spot in the group, 

 the water, though abundant, is brack- 

 ish, but this is susceptible of an ex- 

 planation quite consistent with the 

 experiments of Mr. Witt, which 

 require that the process of perco- 

 lation shall be continued "during 

 long periods and through great masses 

 of porous strata;" Darwin equally 

 concedes that to keep the rain fresh 

 when banked in, as he assumes, by 

 the sea, the mass of madrepore must 

 be " sufficiently thick to prevent 

 mechanical admixture ; and where 

 the land consists of loose blocks of 

 coral with open interstices, the water, 

 if a well be dug, is brackish." Con- 

 ditions analogous to all these parti- 

 cularised, present themselves at 

 Jaffna, and seem to indicate that the 

 extent to which fresh water is found 

 there, is directly connected with per- 

 colation from the sea. The annual 



