W. R. Jones—Tin-mining at Ulu Bakawu, FMS. 455 
_ 2. The bands of tin-ore-bearing rock cannot be taken as evidence 
of parallel lodes, for (1) the intervening rock has not been prospected 
except in a few places on the surface; (2) the actual outcrop of 
bands of rocks of the same strike would all appear as parallel out- 
crops ona hillside, no matter how great the variation in dip may be. 
3. It is proved that the dip of this main lode varies from 15° in 
one direction to 5° in the opposite direction. The simplest explanation 
of such a variation in a faulted igneous rock is a fault, and such - 
faulting is clearly shown in photographs. 
4. What is supposed to be the most convincing argument in favour 
of the horizontal lode theory is the horizontal upper surface of the 
tin-bearing ground shown in photographs.’ 
It will. be noticed, however, that the character of the rock shown 
above this horizontal surface is totally different from the underlying 
rock, and not only is it a much less acid type of granite but it is 
decomposed and contains granite boulders. The junction of the 
unweathered and weathered granite is remarkably sharp and well 
defined, and further evidence is at hand in the adjacent cutting in 
the same hill, on the same level, and within a hundred yards of the 
previous exposure. _ 
The faulting and thrusting caused a landslip which brought down 
the soil from higher up the mountain, smoothed the surface of the 
rock, and gave it the polished surface which it still possesses. Such 
landslips are common even to this day, and two fresh examples. on 
Gunong Raja can be seen from Ulu Bakau. " 
This explanation also accounts for the disturbed and broken character 
of the rock between the fault and thrust planes and, whatis quite 
interesting, accounts for the formation of the steep valley immediately 
below where the rock, broken and crushed by the movement, was 
easily transported by water, leaving the more compact rock to form the 
steep sides of the valley. Such a case also occurs at Gunong Raja, 
‘where one side of the valley is a huge polished perpendicular wall. 
5. Numerous other pieces of evidence against the horizontal lode 
theory could be pointed out on the ground, but perhaps sufficient 
evidence has been given to show that it would be utterly unsafe to 
attempt a calculation of the amount of tin-bearing rock in this hill 
with the facts now available. 
The question can, however, be approached in another and safer 
way, and one which will furnish the Government with a better 
conception of the amount of tin-bearing rock in this part of Ulu 
Bakau. 
Very strong mineralization is to be seen on Messrs. Bibby & Ruxton’s 
property over an extensive area, but in parts the rock is barren of tin- 
ore. ‘he barren areas are considerable, and the amount of non- 
payable cassiterite-bearing rock is also extensive. ‘There is on this 
property, however, sufficient proved ground to give the mine a life 
for many years, and there is every indication of mineralization 
extending right into the mountain and into the adjoining land on 
1 The junction is between a quartz-topaz vein and porphyritic granite.— 
J.B.S. 
