TRANSACTIONS OF SECTION C. 573 



a somewhat lower level, representing a later stage in the deepening of the bed of 

 Lake Oxford and of the Gap. 



The south-westerly advance of the chalky boulder-clay glacier up the Ouse 

 basin, preventing any possible drainage to the east through the Stony Stratford 

 valley, must liave caused the formation of a lake over the comparatively low 

 ground which probably then existed between the Chiltern, the White Horse, and 

 the Cotteswold Hills. That the drainage of this lake was from the first in the 

 direction of the present gorge is shown by the presence of flint gravel immediately 

 above it, near the 400-foot contour ; it occurs also within it at a lower level. Once 

 started, the drainage has continued to run in the same direction to the present 

 day. The swirl of the water, swollen, especially in summer, by the melting of the 

 ice-sheet which lay close at hand, converging constantly to one point, eventually 

 produced the trumpet-shaped opening which forms such a marked feature of the 

 Gap. 



The bottom of the lake, composed of soft Jurassic clay, was gradually deepened, 

 pari pasm with the excavation of the gorge, the deepest part being always, as 

 shown on the contour maps, near the mouth of the latter, where the erosive power 

 of the escaping water was the greatest. 



8. On the Continuous Glacial Period. By M. B. CoTSWORTH. 



The chain of terminal moraines traced by geologists across America and 

 Europe suggest to the author the probability" that they were formed when the 

 districts ranged within measurable distance of the Arctic Circle, and that they 

 afibrd evidence of a gradual shifting of the North Pole. 



Corresponding evidences in other parts of the world tend <o confirm the author 

 in his opinion that the Polar change is still going on. 



The pyramid system of the ancient Egyptians indicates a change of 7° iu 

 nearly 6,000 years, which is less than one-tenth of the speed of the equinoctial 

 precession. 



The vast ice-cap of Greenland, covering 600,000 to 600,000 square miles, and 

 rising to heights of 8,000 and 10,000 feet^ when taken in conjunction with the fact 

 of Dr. Nausen's havmg crossed the Arctic Sea at corresponding latitudes on the 

 Asiatic side, where the sea-ice only averaged 30 feet thick, suggests to the author 

 that a powerful gravitational force is exerted by the weight of land- ice, which may 

 account for a shifting of the Pole. 



TUESDAY, AUGUST 7. 

 The following Papers and Reports were read : — 

 1. Certain Earthquake Relationshijis. By John Milne, D.Sc. F.R.S. 



The object of this Paper was to show the statical and dynamical relationships 

 of earthquakes to earthquakes and other phenomena. A very large earthquake in 

 one district has given rise to earthquakes and volcanic eruptions in neighbouring 

 districts. This suggests the breakdown of a statical balance between two rock- 

 folds. The fact that large earthquakes from time to time occur in groups, although 

 their origins may be iu distant localities, suggests that the crust of the earth is 

 from time to time generally subjected to unusual stresses. The observation that 

 the frequency of this type of earthquake is roughly proportional to the angular 

 ■change in direction of the earth's axis in a given interval of time, gives strength 

 to the suggestion. The mass-displacements which .accompany megaseismic eflbrts 

 may be regarded as the cause or as the result of pole-displacements, or both may 

 result from more general influences, as, for example, elastic deformations, brady- 

 ■seismical activities, erosion and sedimentation, changes in ocean level, and other 



