408 REPORT— 1882. 



century the atteution of geologists was given to the chalk cliffs forming 

 the south coast of England. Mr. "W. Philips read a paper before the 

 Geological Society of London, in 1818,^ describing the various beds of 

 chalk, showing how constant they were in character and composition at 

 points far apart, and, moreover, that corresponding beds were found on 

 the French coasts of the Channel. These views were confirmed by Tie la 

 Beche, in 1821.'- Mr. Hopkins, in 1857, in his account of the structure 

 of the Wealden district and the Bas Boulonnais, deals with the dis- 

 turbances which affected these beds, as well as others, in the south-east of 

 England. The eastern boundary of his ' disturbed district ' passes from 

 Abbot's Cliff to Cape Grisnez, just missing the area which any tunnel 

 through the chalk must traverse. Mr. F. G. H. Price contributed a 

 valuable papei-, in 1876, on the gault and upper chalk near Folkestone; 

 but it is to Mr. Whitaker and Mr. Topley, of the Geological Survey, that 

 we are indebted for most of the facts, which have been acquu-ed during 

 late years, respecting the beds in question, which facts have been pub- 

 lished in the memoirs of the Geological Survey and elsewhere. 



In France, Prof. Hebert, Dr. Barrois, M. Potior, and others have 

 added much to our knowledge of the cretaceous beds in that country. 



In a few words, the following is a summary of our geological know- 

 ledge of the question, as regards the chalk. This is the only formation 

 we need consider, for no other offers equal advantage for the construction 

 of a tunnel. Indeed, through no other formation is a tunnel jiracticable, 

 taking all things into consideration : — • 



Identical beds of chalk are exposed above the gault in the cliffs on 

 the two sides of the Channel. These beds are, on the two shores, similar 

 in composition, contain similar fossils, and vary but little in thickness. 

 Taken as a whole, they have a slight dip to the north-east. They have 

 been found to pass uninterruptedly across the bed of the Cliannel. Borings 

 have shown that the lower beds increase rather than diminish in thickness 

 as they dip below the sea-level to the eastward of their outcrop. 



Position and Line of Tunnel. 



It will be necessary to assume certain requirements to be fulfilled by 

 the tunnel before proceeding to discuss on what line it will be best to 

 make it. I shall assume that — 



1. It will communicate with existing railways in the ordinary way 



by continuous railway, and not, as has been suggested, by shafts 

 and hydraulic lifts. 



2. It will be provided with a means of drainage by gravitation to the 



shore. That is, the water met with in the tunnel should be able 

 to flow by gravitation from the summit level in mid-channel to 

 the shores of the two countries. This is necessary for safety 

 during construction, and for drainage afterwards. 



3. It will be made for two lines of way, and be so designed as to be 



capable of being worked by ordinary locomotives. 



4. The gradient will nowhere exceed about 1 in 80. 



Geology has told us the kind of strata which will be met beneath the 

 Channel. The experience of engineers gained in past works can alone 

 determine through which of these strata, and through what part of them, 



' Tratt suctions. Geological Society of London, vol. 5. 

 2 Ibid., vol. 1. 



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