214 TUNNELING 



dry and not thoroughly disintegrated, the tunnel was timbered 

 through this seam without difficulty. Several similar veins 

 were thus met and passed through, until at a point 285 ft. from 

 the shaft, where after drilling for about 2 ft. through rock a soft 

 green, almost liquid chlorite vein was struck, which began flowing 

 in through the drill holes with great force. These holes were 

 plugged ; but as it was necessary to know what was ahead, and 

 as with 100 ft. of cover between the tunnel roof and the river 

 bottom it was thought that the condition of affairs could not be 

 very serious, it was decided to continue driving ahead without 

 air pressure, and with a timbered heading. To see what the 

 material would do, several hand-holes were put into the rock- 

 face with the object of blasting out a hole about 2 ft. square 

 through the remaining 2 ft. of rock, to the chlorite. Before 

 blasting, however, the precaution was taken to build a bulk- 

 head, some 40 ft. back from the face. On firing the holes an 

 inrush of many yards of material took place, which was finally 

 checked by some rock fragments closing the opening through 

 the rock. After several desperate attempts on the part of the 

 contractors to control this material and make progress, the work 

 was finally abandoned in the latter part of March, and as a 

 4-in. stream of water was now flowing from the heading, pump- 

 ing was discontinued, and the shaft and tunnel allowed to flood. 

 At the New York end work was still being carried on in 

 compressed air. The rock encountered at the other side of the 

 soft seam closely resembled the decomposed material which had 

 been penetrated before, and consisted of alternate layers of 

 feldspar and chlorite, with an occasional vein of quartz. It 

 was quite soft, though requiring drilling and blasting, and 

 eventually it had to be lined. After the heading had been 

 driven about 69 ft. into this rock the company decided, in 

 spite of the uncertainty as to the material ahead, to remove the 

 air pressure, and to call upon the contractors to resume their 

 contract. Upon removing the air pressure, however, the brick- 

 work through the soft seam proved so unsatisfactory in exclud- 



