ing and accumulation of ore from a kind of top-hole, which is represented by the small vein.
The veins are natural fissures in the limestone, having their walls usually clear and well defined, and the adjacent rock is seldom metamorphosed to any noticeable degree. In the Busan hills the lodes have a general N. W and N. S. and strike and dip at angles varying from 20° to 50°, the amount of dip not being a constant in the same lode; but in the Jambusan valley, about a mile distant, a lode was found striking almost due E. and W. and this was at a considerably lower level than the Busan veins, of which a series of four or perhaps five distinct lodes is to be observed cropping out in one spot, each above the other, with short intervals. The lodes at Bidi are said to dip at a very high inclination, but I have had no opportunity of examining this locality. The working face ranges from six feet to a few inches in depth, and the yield of any single vein is very intermittent.
The adventitious minerals, found associated in the vein with the sulphide, are gold and copper in the gangue, and gold, silver, native arsenic and realgar in the ore. The last-mentioned sometimes spots the sulphide of antimony with small pockets of orange-red crystals, and the ore at Bidi is not unfrequently stained red from the same source. The existence of quicksilver also in some form or other is attested by the presence of globules of metallic mercury in the flues of the reverberatory furnaces, where it has condensed after sublimation in the smelting chamber, and has been deposited together with the white oxide of antimony.
In seeking to decipher the geological sequence of events which resulted in the produce of the system of antimony veins in upper Sarawak, the observer is at once brought face to face with rival theories of the production of mineral veins as a whole. There is no evidence to indicate that the antimony lodes derive their metallic contents by any process of segregation from the rock in which they lic, although portion of the gangues may have been locally so derived; and the true interpretation of the phenomena they present is therefore limited to the inquiry, whether the various minerals were injected in molten state into the including fissures, or were deposited gradually and from solution, by the passage of hot spings through the limestone rock. I do not feel competent to give an opinion on a theoretical matter of this kind, which, to be at all reliable, must be founded on a wide knowledge of strictly chemical geology; but I may here state. that M. Gröger, a geologist and mining engineer employed by
