upon the surface 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 Sáoui 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 "Areca-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 obtained 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. During the changes of the monsoons especially, a fever breaks out of so malignant a type that it is very frequently fatal to Europeans.
But, so long as dense forest, creeping plants, and swamps encumber the soil, there can be no country within the tropics favourable to the health of man, and all immigrants or other persons who make a sufficiently long stay in such localities, prepare themselves for being visited by maladies of the most formidable nature, among which fever and dysentery play the most conspicuous part.
Similar conditions are occasionally met with in certain parts of Europe where swamp and uncultivated land are exposed to the influences of a high temperature, of which examples enough are furnished in the malaria of Italy, and the marsh fever of the lagoons of Venice and along the coasts of Istria. And if such visitations make less impression upon us in Europe, it is not that there is little danger, but simply because, as habit is second nature, the regularity of their return has ceased to attract attention.
This is precisely what the English have experienced in the East Indies, it is what the German emigrant is now going through on the banks of the Mississippi and Ohio, in Brazil and in Peru, until the forests are cleared and rendered productive, until, in short, advancing cultivation has dispelled those miasmata, which are inevitably developed amid the undisturbed voluptuousness of nature.
When at certain seasons of the year the vital principles of millions upon millions of organisms begin to be active, they throw off oxygen into the atmosphere, replacing it by absorbing carbonic acid; while, on the other hand, different
organisms, in conformity with known chemical laws, are destroyed under similar conditions, and, under the influence of the atmosphere co-operating with humidity, ferment and become decomposed. From all which processes result products of emanation, which, caught up into the atmosphere and whirled away by the wind, become in their turn the means of nutriment and fertilization to other plants, thus imparting to tropical vegetation that marvellous rankness and super-abundance so fatal to the human frame. But the conditions which produce this tendency in the atmosphere to generate fever are not peculiar to certain localities, or strictly confined to these; they can be averted, and with them the vapours so prejudicial to health may be removed. We have but to raise up a barrier against that mighty all-devouring process of life and vegetation, which imperils our own conditions of existence, we have but to withdraw from the powerful agencies of chemical action the substances undergoing decomposition, to constrain the waters of heaven to follow certain definite directions, to drain every swamp, to clear the forest, to sweep away the dense underwood in order that the wind may wander unchecked over the now fertilized soil, and a wondrous alteration will take place in the climatic conditions of the Nicobar Islands. Of what may be achieved under such circumstances by energy and perseverance, the island of Penang, some 350 nautical miles distant, furnishes the most striking example, which within a very few decades has, by dint of the progressive clearing and cultivation of the
soil, been converted from a den of fever and malaria, a spot shunned by all men as a residence, into one of the most healthy localities in the East, so much so indeed that it has been made a resort for invalids!