CLARK : GLACIAL SECTIONS. 
429 
The previous wet season naturally resulted in some trouble from 
water. The workmen, therefore, were not a little astonished to 
find dry clay in this shaft below 25 feet, becoming quite crumbly 
at 28 feet. Surprise quickly yielded to alarm as a stroke of the 
pick was followed by a violent bubbling in the water they were 
standing in. The men were hastily pulled out, nor would they 
venture down during the next four or five days ; for all this time 
the bubbling continued. It was most violent at the S.W. corner, 
afterwards found to be the highest point of the succeeding bed. 
From careful enquiry it seemed to me that at least a cubic foot 
of gas was given off per minute, or 1500 cubic feet per day. 
But the amount might very well be several times as much ; this 
is certainly a minimum estimate, yet it amounts to about 7000 feet. 
The space required must have been still greater ; for sand grains 
occupy more than half the space they fill ;* and the gas. as we 
shall see later on, could not have been subjected to more than 
twice the atmospheric pressure. 
After the bubbling had ceased the sinking was continued, 
and the sand-bed (c) they had struck was found to reach the drift 
bottom. Here they found a clay-band, upon piercing which fresh 
bubbling occurred. They therefore stopped the hole and tried no 
further. Probably, however, all the air had escaped ; perhaps a 
small amount had been detained in a fold of the clay-bed ; for 
the water which bubbled up was mixed with sand. 
This was the third sand-bed ; the first (a) appeared in shaft I. , 
200 feet to the N.W. by W., 27 feet below the summit level at 
shaft VII., and 10 feet thick. Though the dip was S.E., towards 
shaft II. nothing was seen of it there or in the drift. In the lat- 
ter, however, just beyond shaft II., was sand-bed B, dipping in the 
same direction, which was the reverse of bed C in shaft V. B 
began in the roof of the drift 10 or 12 feet from shaft II., and 
stretched 23 feet along it. On the floor.it beg-an about 12 feet 
* A fine grained sand was found t > remove more than three-fifths of the 
water contained in a vessel. 
