424 Mr. Francis Fox [May 25, 



by actual tunnelling — the work being commenced at the two ends, and 

 by shafts, and the workmen met in the middle. The tunnel was only 

 2 feet in width, and 3 feet in height, except at the probable point of 

 meeting, where the height is 4 feet 6 inches. The length is 1708 feet, 

 and there is a fall of 1 foot in this distance. About the middle of 

 its course there are apparently two false cuts, as if a wrong direction 

 had been taken : but possibly these were intentional, and provided 

 passing places for the workmen and material. 



Pool of 



The Virqws 

 (NaL to Scale- J 



m 



virqi 

 r eU? 



Fig. 2. — Plan of Tunnel from Spring to Pool of Siloam. 



On the soffit of the tunnel is carved an inscription, of which the 

 following is a translation : — 



" Behold the excavation. Now this had been the history of the 

 excavation. While the workmen were still lifting up the pick, each 

 towards his neighbour, and while 3 cubits (4 feet 6 inches) still re- 

 mained to cut through, each heard the voice of the other, who called 

 to his neighbour, since there was an excess of rock on the right hand 

 and on the left. And on the day of the excavation the workmen 

 struck each to meet his neighbour pick against pick, and there flowed 

 the waters from the spring to the pool for a thousand two hundred 

 cubits (1820 feet), and a hundred cubits (151 feet) was the height of 

 the rock over the head of the workmen." 



A Roman engineer gives an account of a tunnel which was being 

 driven under his directions for an aqueduct. And as he was only 

 able to visit the work occasionally, he describes how on one of his 

 visits he found the two headings had missed each other, and he says 

 that had his visit been deferred much longer there would have been 

 two tunnels. 



The accurate meeting of the headings or driftways of a tunnel can 

 only be attained by the exercise of great care, both as regards direc- 

 tion as well as level. 



We need not go very far to find instances of such an error as in- 

 accurate meeting, but there is one well-known case on an important 

 main line in the Midland Counties where the engineers failed to meet, 

 and to this day reverse curves exist in the tunnel to overcome the 

 difficulty. 



To attain this accurate meeting fine wires are hung down the 

 shafts of a tunnel, with heavy plumb-bobs suspended from them in 



