1882.] on the Making and Working of a Channel Tunnel. 129 



not follow because it is ten miles from the shore ta the middle 

 of the tunnel, that therefore the number of trains at ^\'ork at the 

 same time on that ten miles taking materials outwards should be 

 limited to one. And yet no one suggests that upon the Metropolitan 

 and District Eailways, for example, there shall only be one train on 

 the line all the way between Aldersgate Street and the Mansion 

 House. As a fact, there are at one and the same time fifteen or 

 twenty trains upon that distance. Similarly there could be any 

 reasonable number of trains upon the line in the tunnel as its length 

 increased. 



Let us see, however, what this question of the material to be 

 removed amounts to. Assume that the tunnel for one permanent 

 line is to be 14 feet in diameter internally when finished, and assume 

 that it will be lined with material, about which I shall speak presently, 

 1 foot 6 inches in thickness, that would make a 17 feet (of yards) 

 diameter excavation, equal to, not quite, 25 superficial yards. Assume 

 the machine to be making a progress of 2 yards in an hour, that 

 would amount to 50 cubic yards, or not more than a sufficient load 

 for one train, and this would be a rate of progress that would advance 

 a mile in the working days of six weeks, so that about fifteen months 

 would finish the ten miles. 



It may be said that this is taking too sanguine a view of the 

 speed at which the work would go on ; but if this be so no one can 

 suggest that the supposed difficulty of removing the excavated material 

 is being shirked by an under-estimate ; but even as thus stated, it 

 needs only one train an hour. "Well, it may be said, one train an 

 hour is easy enough on an ordinary railway with locomotives, but 

 how is this one train an hour to be got along underground in a close- 

 ended tunnel, where you won't dare to use an ordinary locomotive ? 

 Are you going to do it by horses ? The answer is, No ! Again the 

 compressed air comes to our aid, and you will find that, without the 

 slightest difficulty, compressed air locomotives, which are already in 

 use in works of this character, and, as I shall have occasion to tell you 

 when I consider the permanent working of the tunnel, have been in 

 lengthened use elsewhere, would be employed for these trains. 



I think you must agree with me that there is no practical difficulty 

 about the transport of the material along the tunnel; but, then, 

 the question may be put, how is it to be got to the surface in sufficient 

 quantities ? 



Two modes are available here. One is that the land tunnel (the 

 incline) should be completed first, and that the material should be 

 got up the incline by a locomotive. But as this waiting for the com- 

 pletion of the land tunnel would involve an unnecessary delay, and as 

 it clearly would be better that the works of the land tunnel and of 

 the part under the sea should go on simultaneously, the material 

 would be got to the surface by winding engines. Let us see what 

 that amounts to. You have 50 cubic yards in an hour for each 

 tunnel, that is, 100 cubic yards in an hour for the two; call the 



Vol. X. (No. 75.) k 



