518 Reports and Proceedings — 



favourable situations, for a distance of 12 or 15 miles from the 

 water-partiug of the country. 



This absence of drift on the eastern side might, the author con- 

 siders, be satisfactorily accounted for by supposing that the trans- 

 verse valleys of the chain were, during the glacial epoch, completely 

 blocked up with congealed snow or ice, by which means all com- 

 munications between the opposite sides of the range would be 

 entirely cut off. The southward flow of the ice, which was probably 

 not so thick as to cover the higher portions of the chain, would, on 

 encountering such an obstacle to its progress, be deflected west- 

 wards, and finally debouch into the plains of South Lancashire, and 

 would there deposit on its retreat the debris it contained. 



11. " On the Granitoid and Associated Metamorphic Eocks of the 

 Lake-district." By J. Clifton Ward, Esq., M.A., F.G.S. 



Paet I. On the Liquid Cavities in the Quartz-hearing Bocks of the 

 Lake-district. 



The object of this paper was to examine into the evidence afforded 

 by the liquid cavities of the granitoid rocks of the Lake-district, with 

 reference to the pressure under which these rocks may have consoli- 

 dated. In the first division of the subject the geological relations of 

 the three granitic centres of the district were considered, and it was 

 shown that these several granitic masses probably solidified at depths 

 varying from 14,000 feet to 30,000 feet. The most probable maximum 

 depth for the Skiddaw granite was stated as 30,000 feet ; the maximum 

 for the Eskdale granite 22,000 feet; and for the Shap granite 14,000 

 feet. These maximum depths were arrived at by estimating the 

 greatest thickness of strata that were ever, at one time, accumulated 

 above the horizon of the top of the Skiddaw slates. 



The mode of microscopic examination, together with a description 

 of the precautions taken in measuring the relative sizes of the cavities 

 and their contained vacuities, formed the second division of the paper. 

 It was stated that all the measurements used in the calculations were 

 made from cases in which the vacuity mixed freely in the liquid of the 

 cavity, and an approximately perfect case for measurement was defined 

 to be one in which the outline of the liquid cavity was sharply defined 

 all round in one focus, and in which the vacuity moved freely to every 

 part of the cavity without going out of focus. 



Then followed the general results of the examination. Restricting 

 the measurements to such cases as those above mentioned, the results 

 were found to be generally consistent with one another, and with those 

 previously obtained by Mr. Sorby in his examination of other granitic 

 districts. From the fact that the calculated pressure in feet of rock 

 was in all cases greatly in excess of the pressure which could have 

 resulted from the thickness of overlying rocks, it was inferred as 

 probable that these granitic masses were not directly connected with 

 volcanic action, by which the pressure might have been relieved, but 

 that the surplus pressure was spent in the work of elevation and con- 

 tortion of the overlying rocks. 



Microscopic, combined with field evidence, was thought to indicate 

 that the Shap granite, though mainly formed at a depth similar to 



