﻿viii Proceedings. [October ph, 1904.. 



pressure, and ultimately fill it up. This may be studied in any 

 coal pit where there is a superincumbent pressure, say of more 

 than 1,000 ft. 



The two following illustrations of folding and faulting by 

 relaxation of pressure are presented by the puddle trench of the 

 Langsett reservoir, belonging to the Sheffield Corporation, and 

 by the two reservoirs now under construction on the headwaters 

 of the Derwent by the Derwent Water Board. In the first of 

 these the foldings in question at the bottom of the valley in the 

 shale under the first grit are strongly marked at the surface. 

 These folds gradually disappear, and are based upon a hard 

 black unmoved shale, offering a good foundation, about 60 ft. 

 below the bottom of the valley. This is in the valley of the 

 Little Don. The thickness of rock removed from the bottom of 

 the valley amounts to no less than something like 8,000 ft. of 

 coal measures and millstone grit. In the case of the Derwent, 

 in which the folding is much more marked, and is accompanied 

 by faulting, the thickness of rock removed amounts to at least 

 9,700 ft. (7,200ft. of coal measures, 2,000 ft. of millstone grit, 

 and at least 500 ft. of Yoredale). In this the movement had 

 not extended beyond a depth of 90 ft. In the case of the 

 Derwent reservoir lower down the river there are two systems 

 of folding and faulting, which do not penetrate beyond 60 ft. 

 from the surface. At that point a good foundation is found for 

 the puddle-trench of the embankment. These points are of 

 considerable importance in considering the sites for reservoirs. 

 So far as 1 know they have not hitherto been recognised. 



At the close of the paper Sir William Bailey remarked that 

 in the section of the Ship Canal between Ellesmere Port and 

 Runcorn, the piling up of the excavated material on the bank 

 caused a bulging of the bed of the canal, and raised a mound on 

 the remote side of the Bridgewater Canal. The difficulty, which 

 proved very serious and costly, was not overcome until wood 

 piles were driven into the soft strata underneath the canal, and 

 the embankment disposed in two heaps instead of one. The 

 discussion was afterwards continued by Dr. Lees, Mr. Stromeyer, 

 Dr. Hoyle, Mr. F. J. Faraday, Mr. Bruton, and Mr. T. Thorp. 



