ANOTHER POSSIBLE CAUSE OF THE GLACIAL EPOCH, 1G3 



ability to the action of drift-ice rather than that of a sheet of 

 land-ice. 



It is true that the tendency of the south flowing Arctic current 

 would be to trend towards the Greenland side of the channel, 

 owing- to the effects of the revolution of the earth on its axis, but 

 if Greenland shared, as it probably did, in the general elevation of 

 the east coast of America, the current would be driven moi'e 

 towards the European shore, and the course of the Gulf Stream 

 itself is an evidence that currents can be diverted by geographical 

 or other causes into other than their natural channels. 



This theory also meets another difficulty. Great cold does not 

 necessarily mean abundant snow. A region of evaporation at no 

 great distance is also necessaiy. A heated Siberian sea would 

 afford just such an area as woald be needed to produce a heavy 

 snow-fall in Noi'th-West Europe and ISTorth-East America. "We 

 should thus have every condition for producing a Glacial epoch in 

 these regions. 



This seems to me to supply a simple explanation of this 

 remarkable era, without calling in the help of a Deics ex mdchma 

 such as the theory of cold and warm regions in space, or such slow 

 working agencies as the varying eccentricity of the earth's orbit, a 

 theory whose very supporters admit could only have produced the 

 required effects if favoured by other exceptionally pi'opitious 

 •circumstances. 



Professor W. S. Greslev, F.G.S., of Erie, United States, 

 writes : — 



In response to your kind invitation to add to the discussion 

 upon Dr. E. Hull's paper, proof of which I have read with much 

 interest, I beg to say : — 



1. It seems quite possible that the elevation referred to along 

 the east of North America may have produced the clay-and-debris- 

 filled fissures, known as " clay- veins," by which much of the 

 coal-measures from Pennsylvania to Missouri, but especially in 

 Pennsylvania and West Virginia, are more or less vertically 

 intersected (see my paper, " Clay- Veins vertically intersecting 

 Coal-Measures " in Bull. Geol. Soc. of America, vol. 9, pp. 35-58, 

 copies of which I am sending to the Institute, and also to 

 Dr. Hull). While all the evidence so far collected indicates that 

 the origin of these fissures was long after the Carboniferous 



