The Malay archipelago : the land of the orang-utan ... - Wallace Online

;XVI.] CELEBES. 183The geological structure of this part of Celebes is interesting.The limestone mountains, thougli of great extent, seem to beentirely superficial, resting on a basis of basalt which in someplaces forms low rounded hills between the more precipitousmountains. In the I'ocky beds of the streams basalt is almostalways found, and it is a step in this rock which forms thecascade already described. From it the limestone precii^ices riseabruptly ;and in ascending the little stairway along the sideof the fall, you step two or three times from the one rock on tothe other,—the limestone dry and rough, being worn by theAvater and rains into sharp ridges and honeycombed holes,—thebasalt moist, even, and worn smooth and slippery by the passageof bare-footed jDedestrians. The solubility of the limestone byrain-water is well seen in the little blocks and peaks which risethickly through the soil of the alluvial plains as you approachthe mountains. They are all skittle-shaped, larger in the middlethan at the base, the greatest diameter occuriing at the heightto which the country is flooded in the wet season, and thencedecreasing regularly to the ground. Many of them overhangconsiderably, and some of the slenderer pillars appear to standupon a point. When the rock is less solid it becomes curiouslyhoneycombed by the rains of successive winters, and I noticedsome masses reduced to a complete network of stone, throughwhich light could be seen in every direction. From these mountainsto the sea extends a perfectly flat alluAdal plain, with noindication that water would accumulate at a great depthbeneath it, yet the autliorities at Macassar have sjjent muchmoney in boring a well a thousand feet deej) in hope of gettinga supply of water like that obtained by the Artesian wells inthe London and Paris basins. It is not to be wondered at thatthe attemjDt was unsuccessful.Retui'niug to my forest hut, I continued my daily search afterThe weather however became dreadfully hotbirds and insects.and dry, every drop of water disappearing from the poolsand rock-holes, and with it the insects which frequented them.Only one group remained unaffected by the intense droughtthe Diptera, or two-winged flies, continued as plentiful as ever,and on these I was almost compelled to concentrate my attentionfor a week or two, by which means I increased my collection ofthat Order to about two hundred species. I also continued toobtain a few new birds, among which were two or three kindsof small hawks and falcons, a beautiful brush-tongued jDaroquet,Trichoglossus ornatus, and a rare black and white crow, Corvusadvena.At length about the middle of October, after several gloomydays, down came a deluge of rain, which continued to fall almosteveiy afternoon, showing that the early part of tlie wet seasonhad commenced. I hoped now to get a good liarvest of insects,and in some respects I was not disappointed. Beetles becamemuch moi'e numerous, and under a thick bed of leaves that had