A coarse conglomerate is also to be seen intervening between beds of the claystone, imbedding angular fragments of many descriptions of igneous rocks and workable porphyry, which is also quarried and made use of for pillars, blocks for corn-mills, basement slabs, &c." - Calcutta Journal of Nat. Hist., vol. ii. p. 136.
As characteristic features in the island, may be mentioned the absence of rivers, lakes and forests. The valleys are fertilized by numerous streamlets communicating with narrow canals, which traverse the island, and serve both for agricultural purposes as well as means of communication for want of carriage-roads. All the canals, at least in several miles distance round Ting-hae, the principal city of the island, discharge their surplus into a common canal, which passing through the city communicates with the sea.
The entire absence of forests appears to be of a comparative recent date, to judge from certain passages in a letter written by Mr. Cunningham in the year 1701, in which deer are mentioned as being in abundance, which circumstance would presuppose a woody appearance of some part of Chusan at least. The writer says, "The island in general abounds with all sorts of provisions, such as cows, buffaloes, goats, deer, hogs, wild and tame geese, ducks and hens, rice, wheat, calavances, coleworts, turnips, potatoes, carrots, beetach and spinach. Here also the tea grows in great plenty on the tops of the hills, but it is not in such esteem as that which grows on more mountainous islands. Although this island is pretty well stored with people, it is far from what it was in P. Martini's time, as he describes Chusan. The rest of the circumjacent islands are either desert or meanly inhabited by a few people, but all of them stored with abundance of deer, for it is not long since Chusan began to be peopled. It is true in Martini's days, about fifty years ago, it was very populous for the space of three or four years, at which time the fury of the Tartar conquest was so great that they left it desolate, not sparing so much as the mulberry-trees (for then they made a great deal of raw silk here); and in this condition it continued till about eighteen years ago." - Extracted from Harris's complete collection of Voyages in Chinese Repository, vol. ix. p. 133.