King — On the Jointing of Bodes in Relation to Engineering. 571 



anticlinal. I am more inclined to take the view that they were origin- 

 ally equatorial and meridional joints existing previously to the up- 

 heaval, some having been widened so as to resemble crevices, and others 

 converted into the faults common in the district. This view^ may be 

 taken as strongly supported by the fact that jointing of both systems 

 are to be seen within the area under consideration, occurring in beds 

 that can only have been slightly disturhed. JS^ear St. Leonards, one of the 

 wealden members, lying below high- water mark, is distinctly divided 

 by both meridional and equatorial jointing in its typical form ; and, to 

 all appearance, it seemingly has no more resulted from stratic dis- 

 turbances than the corresponding structures so wonderfully developed 

 in the nearly horizontal limestones in the Burren of Co. Clare. 



On the opposite parts of Prance clear evidences occur in the chalk 

 rocks of the same coincidences between jointing, faults, &c., highly 

 calculated to give rise to serious apprehensions in connexion with the 

 tunnel. M. Daubree* has mapped the river-drainage of the district 

 watered by the lower part of the Somme, which, it is well known, 

 takes two main directions, approximately !N".E. to S.W. and N.'W. to 

 S.E. He has also determined these bearings to be in parallelism with 

 two systems of fracture referable to those of jointing. 



If further evidences adverse to the Channel Tunnel be called for, 

 I would urge anyone to consult M. Daubree's figures and description of 

 a long stretch of coast near Treport, north of Dieppe, occupied by 

 chalk-cliffs, crowded with vertical jointing belonging to the same in- 

 tersecting systems; also to examine the ''many small faults" and 

 "very marked and constant joints" which characterize the chalk-cliffs 

 in many places near Margate,^ and the " numerous nearly vertical cre- 

 vices" intersecting a bed of chalk fifty feet thick close to Lover, at the 

 base of Shakespeare's Cliff.° 



The cases above noticed are sufficient to show the strong proba- 

 bility that the chalk rocks to be penetrated are more or less affected by 

 sources of water leakage : indeed it may be contended that, what with 

 inclined bedding partings, faults, disruptive fractures, true jointing, 

 swallow holes and rocli-porosity , the engineers of the Channel Tunnel 

 will have a serious work in hand. 



That the tunnelling of the Strait of Dover is expected to bring out 

 adverse contingencies is evidently anticipated, as some of the engineers 

 have proposed to line the work with blocks of concrete, formed of chalk 

 on the spot, and gravel from a distance. But it is extremely doubtful 

 that this material would have sufficient strength, or power of resist- 



^ Prof. Haiighton, M. Daubree, and others, talte the mechanical view as to the 

 origin of jointing. Prof. Phillips (whom I follow) leaned to what may be called 

 the physical view. 



* Etudes Synthetiques de Geologie, pram, partie, 324-326, 360. 



5 W. Whitaker, Q. J. Geol. Soc, vol. xxi., p. 396. 



s W. Phillips, iV««s. Geql. Soc, 1st S., vol. v., p. 34. 



R. I. A. PKOC, SEK. II., VOL. Ill, — SCIENCE. 3 C 



