are not, as others suppose, occasioned by the falls of heavy rains that deluge the country for one half of the year; which is likewise to be inferred from many of them having no apparent outlet and commencing where no torrent could be conceived to operate.  The most summary way of accounting for this extraordinary unevenness of surface were to conclude that, in the original construction of our globe, Sumatra was thus formed by the same hand which spread out the sandy plains of Arabia, and raised up the alps and Andes beyond the region of the clouds.  But this is a mode of solution which, if generally adopted, would become an insuperable bar to all progress in natural knowledge by damping curiosity and restraining research.  Nature, we know from sufficient experience, is not only turned from her original course by the industry of man, but also sometimes checks and crosses her own career.  What has happened in some instances it is not unfair to suppose may happen in others; nor is it presumption to trace the intermediate causes of events which are themselves derived from one first, universal, and eternal principle.

Causes of this inequality.

To me it would seem that the springs of water with which these parts of the island abound in an uncommon degree operate directly, though obscurely, to the producing this irregularity of the surface of the earth.  They derive their number and an extraordinary portion of activity from the loftiness of the ranges of mountains that occupy the interior country, and intercept and collect the floating vapours.  Precipitated into rain at such a hight, the water acquires in its descent through the fissures or pores of these mountains a considerable force which exerts itself in every direction, lateral and perpendicular, to procure a vent.  The existence of these copious springs is proved in the facility with which wells are everywhere sunk; requiring no choice of ground but as it may respect the convenience of the proprietor; all situations, whether high or low, being prodigal of this valuable element.  Where the approaches of the sea have rendered the cliffs abrupt, innumerable rills, or rather a continued moisture, is seen to ooze through and trickle down the steep.  Where on the contrary the sea has retired and thrown up banks of sand in its retreat I have remarked the streams of water, at a certain level and commonly between the boundaries of the tide, effecting their passage through the loose and feeble barrier opposed to them.  In short, every part of the low country is pregnant with springs that labour for the birth; and these continual struggles, this violent activity of subterraneous waters, must gradually undermine the plains above.  The earth is imperceptibly excavated, the surface settles in, and hence the inequalities we speak of.  The operation is slow but unremitting, and, I conceive, fully capable of the effect.

Mineral productions.