Reports and Proceedings — Geological Society of London. 383 



Another feature which may be mentioned is her description of 

 several examples in the Dolomites where there had apparently 

 been a local reversal of the regional westward movement, and her 

 reference to the familiar examples of eastward overthrusts in the 

 Judicarian district, and on the eastern and south-eastern front of 

 the grander mountain massives of the Swiss and French-Italian 

 Alps. While each individual case demands special examination, she 

 indicates an explanation that satisfies certain cases which she has 

 examined. At localities where the base of the thrust-mass is open 

 to inflows of igneous rock, the igneous material may ascend and be 

 carried onward with the gliding mass, undergoing consolidation 

 during the movement, and inducing contact changes in neighbouring 

 rock material. After consolidation of such igneous inflows, they 

 present resisting bodies within the thrust-mass, which, in the same 

 way as any massive developments of hard sedimentary material, 

 impede the advance of rock material in the same direction as before, 

 and thus cause local deflections. The tendency is for the material of 

 the thrust-mass to be strongly plicated and faulted as it is driven 

 -against any such resisting bodj^ widening out in a direction roughly 

 parallel with the resisting mass, and piling up the material in front 

 to such an extent that local reversal of the direction of overlapping 

 is produced. 



2. " The Influence of Pressure and Porosity on the Motion- of 

 Sub-Surface Water." By William Ealph Baldwin- Wiseman, M.Sc, 

 Assoc. M. Inst. C. E., F.G.S. 



The author commences the paper with a brief historical summary 

 of the researches which have been conducted since 1830 on the 

 motion and behaviour of underground water, more especially dealing 

 with the question of sub-surface flow and the delimitation of cones 

 of depletion. 



In the second part of the paper, in discussing the influence of 

 the porosity of a rock, on the rate of flow of water through it, he 

 describes in detail the variations in porosity which may occur in 

 restricted areas of the same rock, due to superincumbent pressure, 

 faulting, and the intrusion of dykes, illustrating the various points 

 with data collected in the field. He also discusses and describes 

 experiments on the rate of desiccation and soakage of various rocks. 



He then describes a lengthy series of laboratory experiments, 

 which he conducted with "specially devised appai*atus of his own 

 design to aiford a constant pressure and to eliminate all possible 

 errors due to lateral flow, and in which he demonstrates that there 

 is not a uniform relation between flow and pressure in various rocks 

 over a considerable range of pressure, and discusses the various 

 phenomena which were manifested. 



In the third portion of the paper he describes the various attempts 

 at determining the range of the cone of depletion in various strata, 

 and then proceeds to outline a method based upon an experimental 

 determination of the variation of internal pressure in a rock mass 

 when charged with water and subjected to a considerable diflference of 



