All these streams are liable, during the fury of the monsoons, to be surcharged with rain till they overflow their banks, and spread in wide inundations over the level country.  On the subsidence of these waters, the intense heat of the sun acting on the surface they leave deserted, produces a noxious and fatal malaria.  Hence the rivers of Ceylon present the curious anomaly, that whilst the tanks and reservoirs of the interior diffuse a healthful coolness around, the running water of the rivers is prolific of fevers; and in some seasons so deadly is the pestilence that the Malabar coolies, as well as the native peasantry, betake themselves to precipitate flight.[1]

[Footnote 1:  It has been remarked along the Mahawelli-ganga, a few miles from Kandy, that during the deadly season, after the subsidence of the rains, the jungle fever generally attacks one face of the hills through which it winds, leading the opposite side entirely exempted, as if the poisonous vapour, being carried by the current of air, affected only those aspects against which it directly impinged.]

Few of the larger rivers have been bridged, except those which intersect the great high roads from Point-de-Galle to Colombo, and thence to Kandy.  Near the sea this has been effected by timber platforms, sustained by piles sufficiently strong to withstand the force of the floods at the change of each monsoon.  A bridge of boats connects each side of the Kalany, and on reaching the Mahawelli-ganga at Peradenia, one of the most picturesque structures on the island is a noble bridge of a single arch, 205 feet in span, chiefly constructed of satin-wood, and thrown across the river by General Fraser in 1832.

On reaching the margin of the sea, an appearance is presented by the outline of the coast, near the embouchures of the principal rivers, which is very remarkable.  It is common to both sides of the island, though it has attained its greatest development on the east.  In order to comprehend its formation, it is necessary to observe that Ceylon lies in the course of the ocean currents in the Bay of Bengal, which run north or south according to the prevalence of the monsoon, and with greater or less velocity in proportion to its force at particular periods.

[Illustration:  CURRENT IN THE NE MONSOON.]

In the beginning and during the strength of the northeast monsoon the current sets strongly along the coast of Coromandel to the southward, a portion of it frequently entering Palks Bay to the north of Ceylon; but the main stream keeping invariably to the east of the island, runs with a velocity of from one and a half to two miles an hour, and after passing the Great Bass, it keeps its course seaward.  At other times, after the monsoon has spent its violence, the current is weak, and follows the line of the land to the westward as far as Point-de-Galle, or even to Colombo.

[Illustration:  CURRENT IN THE S.W.  MONSOON]