380 On the intended Thaincs Archway 



discharged a great quantity of sand and water into the drift. 

 At the time this circumstance happened, a space of only six 

 inches by thirty of earth in the roof and none in the face 

 was left untimbered; and through this space the earth kept 

 falling by degrees, until a hole was formed capable of letting 

 a man stand up in it ; who observed a quicksand, about 

 three feet thick, and about four or five feet above the roof 

 of the drift. The stratum between the drift and sand was 

 clay ; water flowed from the sand. The hole was after some 

 difficulties filled up, and the works proceeded. 



From the observations which had been made in the pro- 

 gress of the drift, the engineer found that the strata dipped 

 slightly from the south to the north, and concluded that the 

 gravelly stratum No. 2 in the shaft would end in quicksand. 

 This inference was confirmed by borings in the north siifre 

 at E, and by the fact that the wells there are much deeper 

 than on the south. In expectation therefore of drawing off 

 the water from the face of the work, borings were made at 

 D, through the roof of the drift, and pipes forced up to the 

 top of the quick-sand, which had the desired effect. The 

 water came free from sand for a considerable time; but 

 when the sand began to come through any of the pipes they 

 were plugged up, and others occasionally inserted in diffe- 

 rent places to the south of these, with the same object in 

 view ; and which kept the face of the work dry. By this 

 means, and by using the utmost precaution in all other re- 

 spects, the drift was afterwards extended seventy feet be- 

 yond this fracture; where the roof broke down a second 

 time, and sand and water entered the drift-way with great 

 violence, and to an alarming degree ; so that in about a 

 quarter of an hour the water rose in the shaft nearly to the 

 top of it. On examining the river an opening or hole at w 

 was discovered in the bed, of about four feet diameter and 

 pine feet deep, and its sides nearly perpendicular. Into this 

 hole, clay partly in bags, and other materials, were thrown 

 sufficient to fill it up ; and which succeeded in stopping the 

 communication between the river and the drift. The face 

 pf the drift was again opened; but the men could make but 

 little progress, as the water and sand frequently burst in 



Vi.pon, 



