76 ' SPOLIA ZEYLANICA. 



This, one may suppose, has always happened, as it is now happen- 

 ing, each river carrying to the coast from the inland vast loads of 

 detritus on every day that it is affected by the monsoon rain — 

 material which, on reaching the coast, has been carried by the 

 sea currents and deposited until it has formed the outline of the 

 shore that we now see, an outline which it is still extending and 

 altering. 



The method of extension seems to be, first, the formation of bays 

 along the coast, by the gradual banking up of sand and detritus at 

 some little distance from the shore Hne, banks originally induced 

 perhaps by some obstacle, such as a slight rocky ridge. The 

 banking process seems to continue until the bay becomes a lake — 

 at first salt, then more and more brackish by degrees, and finally, 

 after many monsoons, perfectly fresh. 



The succeeding process would no doubt be that such a lake would 

 slowly fill up witli vegetable humus and detritus due to the rains, 

 until it assumed its final stage as a sHght depression in the land or 

 as a swamp. 



Note should here be made of the fact that the coast extension 

 work probably takes place chiefiy during the south-west monsoon 

 period on the western side and during the north-east monsoon on 

 the eastern, for it is during these periods that the heaviest rainfall 

 occurs in each case, bringing the necessary material down to the 

 coast. 



(2) There is, however, a marked difference to be noticed in the 

 results, due to the different character of the two monsoons. 



The south-west monsoon rains, speaking generally, fall steadily 

 and constantly, and the greater amount of moisture in the air 

 throughout the year on the western side of the Island induces a dense 

 vegetation, which tends to hold together the particles of soil. 



The north-east monsoon rains, on the other hand, though less 

 in total amount, fall with great violence and suddenness on a soil 

 which has for several months been exposed to the action of a fierce 

 unclouded sun and an intensely dry air, so that it is in a defenceless 

 condition against the momentum of the sudden torrents of water 

 by which it is assailed. 



It is probable, therefore, that a larger amount of detritus is carried 

 down to the eastern coast than to the western, thus occasioning a 

 larger number of lagoons on that side ; and also the fact that the 

 low-country, taken as a whole, is more extensive on the eastern side 

 of the mountains than on the other. There are, besides, many more 

 water-courses from the hills to the eastward to bring down material, 

 though many of them cease to flow during the dry season. 



(3) The fact that the lagoons of the northern side are still open 

 to the sea is probably due to the much greater distance that the 

 material has now to be carried from the hills, the freshets not being 

 sufficiently strong to carry it, except, as it were, in loads, a bit at a 



