(Footnote.  The largest I have seen was brought from Tappanuli by Mr. James Moore of Arno’s Vale in the north of Ireland.  It is 3 feet 3 1/2 inches in its longest diameter, and 2 feet 1 1/4 inches across.  One of the methods of taking them in deep water is by thrusting a long bamboo between the valves as they lie open, when, by the immediate closure which follows, they are made fast.  The substance of the shell is perfectly white, several inches thick, is worked by the natives into arm-rings, and in the hands of our artists is found to take a polish equal to the finest statuary marble.)

Rivers.

No country in the world is better supplied with water than the western coast of the island.  Springs are found wherever they are sought for, and the rivers are innumerable; but they are in general too small and rapid for the purpose of navigation.  The vicinity of the mountains to that side of the island occasions this profusion of rivulets, and at the same time the imperfections that attend them, by not allowing them space to accumulate to any considerable size.  On the eastern coast the distance of the range of hills not only affords a larger scope for the course of the rivers before they disembogue, presents a greater surface for the receptacle of rain and vapours, and enables them to unite a greater number of subsidiary streams, but also renders the flux more steady and uniform by the extent of level space than where the torrent rolls more immediately from the mountains.  But it is not to be understood that on the western side there are no large rivers.  Kataun, Indrapura, Tabuyong, and Sinkel have a claim to that title, although inferior in size to Palembang, Jambi, Indragiri, and Siak.  The latter derive also a material advantage from the shelter given to them by the peninsula of Malacca, and Borneo, Banca, and the other islands of the Archipelago, which, breaking the force of the sea, prevent the surf from forming those bars that choke the entrance of the south-western rivers, and render them impracticable to boats of any considerable draught of water.  These labour too under this additional inconvenience that scarcely any except the largest run out to sea in a direct course.  The continual action of the surf, more powerful than the ordinary force of the stream, throws up at their mouths a bank of sand, which in many instances has the effect of diverting their course to a direction parallel with the shore, between the cliffs and the beach, until the accumulated waters at length force their way wherever there is found the weakest resistance.  In the southerly monsoon, when the surfs are usually highest, and the streams, from the dryness of the weather, least rapid, this parallel course is of the greatest extent; and Moco-moco River takes a course, at times, of two or three miles in this manner, before it mixes with the sea; but as the rivers swell with the rain they gradually remove obstructions and recover their natural channel.