146 Records of the Geological Survey of India, [vol. X, 
The fifth cross-cut is entirely in shale, beyond which, at the end of the drift, is the 
sandstone (a). 
About 80 feet south-west of the fourth cross-cut the seam is exposed in a surface 
outcrop. It has a thickness of not less than 10 feet, and dips about south-20°-east at 30°. 
I do not think that this is the true dip, however, hut merely a bending over of the seam 
at the outcrop caused by a slip of the surface debris, &e. 
Thirty yards further the following section is exposed— 
(a)—Sandstone, seen 
Ft. 
10 
In. 
0 
(b) — Brown shale 
1 
0 
(c)— Coal 
... 
1 
0 
(d) — Brown shale 
3 
0 
(e)—Coal 
12 
6 
(/) — Brown shale 
0 
9 
(g)— Sandstone, seen 
8 
0 
Dip about south at 60.° 
Throughout, then, the length of 250 feet in which the seam is traceable, it possesses 
a fair degree of uniformity in thickness. But the strike twists round from south-15°- 
west to west, or through 75°; while the dip, which is 80° at one end, is an inverted 
one of 60° at the other, the difference being 40.° Of course these are merely local features 
affecting one portion of one seam, but my experience of the rocks generally does not 
lead me to suppose that the beds at Tindharia are subject to any unusual degree of dis¬ 
tortion. Taking into account, then, that the Tindharia seam is thicker, and perhaps more 
uniform in thickness, than any yet found, it is manifest what extreme difficulty the condition 
of the rocks in question must oppose to any attempt at mining the coal seams generally. 
Necessity for timbering .—The experience gained shows also that galleries cannot be 
driven into the coal for a single yard without complete timbering ; on which, owing to the in¬ 
coherent, non-self-supporting character of the coal, an unusually heavy pressure is put (which 
is shown by ‘ creep’ of the floor of the gallery as well as by bulging in of the sides and roof); 
and owing to the heat and damp within the drift, the wood quickly becomes unserviceable 
from rot. With the comparatively trifling superincumbent weight of 40 or 50 feet of 
rock, some of the 3-inch planks wore beginning to yield at the time of my visit; and 
Mr. Tyndall informed me that it was frequently necessary to renew them here and there, while 
a complete renewal would be necessary if it wore decided to carry the work on further. 
No doubt the timber would last longer in a regular mine with an organized system of ven¬ 
tilation ; hut making every allowance for this, it is certain that the expense for timbering 
in any mines in the Darjiling coal would be extremely heavy. 
Fire-damp .—11 has also been shown that the coal is not altogether tree from fire¬ 
damp, two slight explosions having occurred during the progress of the drift. There would 
be little to fear, however, on this score in regular mining operations, as the usual amount 
of ventilation would doubtless^ be more than sufficient to carry off the small amount of gas 
generated. 
Coking properties of coal .—Some time ago a quantity of the coal was sent by 
Mr. Tyndall to Calcutta, and through the courtesy of Mr. Blackburn, Manager of the 
Oriental Gas Company’s works, Mr. Medlicott and myself were enabled to experiment on 
its coking properties, in some gas retorts placed at our disposal. 
