Absence of Mmcval Springs. — Monsoon Fever. 91 



ing upon the sui'face of the sea- water, which is heavier, while 

 the porous coral rock prevents the complete intermixture 

 of the salt and fresh water. In the villages of Moose and 

 Saoui on Kar-Nicobar we saw several such cisterns, which 

 always had eight or ten feet good fresh water. Of rivers, 

 properly so called, we found but two, one falling into the 

 northern Bay of Kar-Nicobar, the other at the southern point 

 of Great Nicobar. The former, which from the luxuriant 

 growth of the cabbage tree along its banks we named 

 " Ai'eca-river," is navigable for flat-boats for about two miles 

 from its mouth, at which point further progress is arrested by 

 some small rapids. Here the water is quite sweet, holding 

 but a very little chalk in solution. 



We found no mineral waters or warm springs. The 

 hardened marl deposits of Nangkauri harbour we perceived 

 however to be encased in a crust an inch thick of sulphate of 

 magnesia, and fine silk-like glistening fibres ; this results from 

 the clay-marl containing sulphate of magnesia, so that very 

 possibly by digging cistern-shaped cavities, a bitter saline 

 solution might be obtained similar to that at present ob- 

 tained under similar circumstances at Billin in Bohemia. 



In consequence of the extraordinarily rich vegetation, the 

 dampness of the soil, and the numerous mangrove swamps all 

 along the coast, the climate, as may readily be conceived, is 

 at present anything but salubrious. Dm'ing the changes of 

 the monsoons especially, a fever breaks out of so malignant 

 a type that it is very frequently fatal to Europeans. 



