18 
Records of (lie Geological Survey of Tndia. 
[vol. IX. 
suggest to make straight for the nearest point of the slope of the ridge, but it must be 
modified in this case. I have carefully examined the line of the surface, and should con¬ 
sider that course to be unsafe; the slope to the south is too near and too rapid. The ground 
from which a supply is to be expected lies to the west and west-south-west. I would recom¬ 
mend that the drift be cut to west-30 0 -south, with a rise of 1 in 20. This direction, too, 
would approximately suit the probable run of the strata. 
13. There is at least one advantage in having the well in solid rock ; it may be left 
with its present full width, and only cased for 20 feet or so from the surface. I would 
recommend that this be done at once; and that the pump, by which it is to be hoped the 
future water-supply is to be raised, be put in position now. In such a well, too, the work 
can be continued at any time as well as at first, should a season’s trial prove the supply to be 
insufficient. 1 would not, however, let this be an excnse for an incomplete job at first; the 
failure would, of course, occur in a season of extreme drought, and might be seriously felt. 
But, indeed, the energy of Dr. Coates has provided an excellent resource for a time of such 
need, by converting the unsightly and doubtfully salubrious ravine in front of the Peni¬ 
tentiary into a most picturesque lake of deep water. A very little care on the part of the 
authorities can prevent any possibility of its becoming unwholesome. 
14. The case of the Central Jail well is quite analogous to that of the Penitentiary, 
but a little more puzzling. Here too, however - , I would recommend the prosecution of the 
work. I believe that success can be secured at a much less cost than would be entailed by 
abandoning the site upon which preparation and work has been already so far expended. 
At top there were 6 to 8 feet of red gravelly earth, resting on the edges of the strata, 
which are thoroughly disintegrated for 3 to 4 feet passing down into much firmer rock. 
Unlike in other wells the beds here have a steady dip of 4Cr to nortlr-35°-west. At a depth 
of 30 feet on the rise, and 38 on the fall, an intensely hard rock was encountered, in which 
the work now stands at 40 feet. This well also had just heen unwatered; and considering 
this, and the time of year, the leakage appeared to me to be very' trifling. The last rock 
cut in this well is exceedingly' unpromising ; the large surface of it now exposed does not 
show a single crack or crevice. It breaks with sharp edges and large eonchoidal fracture : 
it is a fine grained mixture of hornblende quartz and felspar thoroughly crystallized ; super¬ 
ficially it might be described as a granitic diorite; but geologically it must come under the 
genus gneiss, as it seems to be strictly in the bedding, and to be simply an exaggerated form 
of the fine foliated homblendic gneiss of the district. A correct knowledge of this rock 
would greatly help a decision regarding the well; but very little can be discovered; there 
is no out crop of it to be found. On the other side of the Penitentiary, at the edge of the 
upper lake, on exactly similar rock is exposed for fully 10 yards across its strike. Thus in 
the well shaft there is a prospect of having to cut through an indefinite thickness of perfectly 
barren rock, and of the most difficult nature. The same obstacle affects the consideration of 
a drift. In this position, also, the condition of the surface is of dominant importance on 
account of the rapid fall in certain directions. The most likely direction for a drift to inter¬ 
cept an abundant supply of water would be about due south, but this would take it into 
the same rock, and even for a greater thickness than in the shaft, the cut being oblique both 
to the strike and the dip ; here, however, there would be the prospect of its becoming softer 
at every step. I have no doubt of this being the safest course. The lower the inclination 
of the drift, the hotter the chance. I would not advise a greater slope than would ensure 
the flow of water to the shaft. By cutting the drift to northward, it would run towards a 
convex bend of the ridge, and success would not be so secure ; but the obnoxious rock (at 
least this bed of it) would be avoided. 
15. There is one well in a position to be compared with these. The well for the 
Police Barrack stands nearly centrally on the ridge of which the new buildings occupy pro¬ 
longations : it is 470 yards to west-18°-nortli from the Penitentiary well (the distances are 
taken from a plan lent, to me by Colonel Dawson) and 1 foot 9 inches higher; the same well 
is 700 yards to south-42°-west from the Central Jail well, and 4 feet 6 inches above it. 
It is 30 feet deep. I have had very different accounts of this well: like all the others, it 
fills to tlie brim in the rains, and some say that it has a constant supply, the demand upon 
it not being very great; while others declare that it fails ; that in the hot weather people 
living along side it fetch water from a considerable distance in the hollow. Some measure¬ 
ments of these three wells are given in Table II. The water in the two new wells on the 
10th October was probably below what they had contained at their fullest; but even that 
