434 Mr. Francis Fox [May 25, 



The time taken for each portion of the attack in the hard Anti- 

 gorio gneiss, is as follows : — 



Bringing up and adjustment of drills 20 minutes. 



Drilling If to 2 J hours. 



Charging and firing 15 minutes. 



Clearing away de'bris 2 hours. 



or a total of between 4^ to 5^ hours, resulting in an advance of 

 3 feet 9 inches, or a daily advance of nearly 19 feet 6 inches. 



The progress of each of the two faces during the month of April 

 last has averaged 17 feet 3^ inches per day, and is a remarkable 

 corroboration of the speed estimated by the engineers four years ago. 

 The estimate was as follows : — 



1st year, the daily progress at each face would be 8*85 feet 



2nd „ „ „ „ 17-22 „ 



3rd „ „ „ „ 19-18 „ 



4th „ „ ,. „ 21-32 „ 



5th „ „ „ „ 31-16 „ 



The work is now in its second year, so that the estimated speed 

 is being exceeded. In other words, the tunnel is being driven 

 through granite at a higher speed than is attained in London clay. 



Water power is abundant, and the waters of the Ehone are har- 

 nessed to the work, whilst those of the " Diveria " provide the power 

 at Iselle. 



Views are given of the intake from the Ehone, the concrete 

 aqueduct, the metallic conduit pipes, 3 feet, and 3 feet 3 inches in 

 diameter, which carry a pressure of 250 lbs. to the inch. The 

 further necessary increase in pressure is obtained by high pressure 

 pumps in the power house. 



It was at one time intended to sink a 20-inch bore-hole from the 

 village of Berisal to the tunnel, a depth of some 2400 feet, for the 

 purpose of delivering water at high-pressure for the works. This 

 may still be done, but the meandering of the tool might result in the 

 awkward dilemma of having to search for it, in solid rock, below 

 ground. 



Some few years ago a rather amusing incident occurred in con- 

 nection with a tunnel, which is worth recording. A certain railway 

 company were constructing a tunnel beneath and nearly at right 

 angles to an existing tunnel of one of the large English railway 

 companies. As the legal formalities were not actually completed the 

 engineers were requested to stay proceedings until all was in order, 

 and they instructed the contractors accordingly, but the latter were 

 anxious not to incur any delay, and they quietly and surreptitiously 

 continued to drive their heading through. The engineer of the 

 existing railway suspected this, and sank a bore-hole on the centre 

 line of the new work, expecting his tool would, at the correct level, 

 drop into the heading, at a depth of 70 feet. The contractors looked 



