1882.] on the MaJcing and Working of a Channel Tunnel. 133 



out by it, for by the hypotbesis, tbe grey cbalk being impermeable, 

 there is no fresh water in it to flow outwards, and no salt water could 

 continue to flow through it inwards, for there is nowhere for it to 

 go to. There must be therefore an entirely stagnant condition within 

 this fissure. It is not suggested that the water of the English Channel 

 is free from sedimentary matter. Granted this state of things, it 

 appears to me to be inevitable that in process of time such a fissure, 

 having in it stagnant water, must have been filled up with the de- 

 positable matter that is in the sea, and must thereby have become 

 closed and puddled up. I therefore look upon it as practically im- 

 possible that there can be any open fissure, which would let down the 

 sea water through the grey chalk. Even, however, assuming there 

 were an open fissure, one thing is quite certain, no destruction of life 

 among those engaged in the work of the heading need ever take place 

 from such a cause, because it is perfectly practicable to keep a trial- 

 hole of about two inches in diameter 10, 15, or 20 feet ahead of the 

 princij)al excavation, the tool for this hole passing up through the 

 hollow shaft of the machine and being worked by it. The tool itself 

 would also be hollow, and if any water were met with it would show 

 itself by issuing through the small hole in the centre of the tool, and 

 thus ample warning would be given. Further, such a tool would enable 

 the width of the fissure to be ascertained ; and I, for one, believe it 

 to be within the power of the engineers of the present day, with the 

 means and appliances they have at hand, to bridge a fissui'e even 

 under a pressure of some 150 lbs. to the incb, if the fissure were 

 not many feet in width ; and if it were, then there is a mode other 

 than bridging, by which such a fissure could be traversed. 



I have shown you how it is, that the occurrence of a fissure need 

 not lead to disaster by an unexpected giving way of the heading, and 

 the influx of the sea water. This of course refers to the question of 

 the experimental heading, for when the experimental heading is once 

 through, then we may be said to know all about the nature of the 

 stratification, and all uncertainty, and all danger of surprise are at an 

 end. Perhaps you may think it well, that instead of the mere bare 

 statement that if a fissure did occur it could be dealt with, I should 

 give you some detail upon the subject. I will now do so, and I will 

 deal with it in connection with the 7-foot diameter trial heading. 



A fissure must either be wide or narrow. If it be wide it occurs 

 as a wide opening at the bottom of the sea (a thing that I believe 

 could not exist without having been detected by soundings). Under 

 such conditions it would be perfectly practicable to lower material 

 into it at the place where the heading is to be made — for example, 

 neat Portland cement — and thus to close the fissure, making an 

 artificial rock to be cut through, but I presume no one believes 

 that any such fissure as this exists. As you are aware, I do not 

 believe that any unclosed fissure at all exists. But I will come 

 now to the case of a narrow fissure, one that we could not localise 

 at the bottom of the sea sufficiently to deal with it in the way of 



