Searles V. Wood—The Cause of the Glacial Period. 295 
in excess of the sun’s melting power, in or contiguous to the particular 
region in which it is found, no evidence of an ice cap having occupied 
the Arctic circle during the Glacial Period has been detected by the 
geologists whose attention has been directed to the most northern 
parts of America yet examined geologically, with any approach to 
minuteness.* 
It was thus therefore that the areas of greatest present rainfall in 
Britain, viz. Westmoreland, Cumberland, Wales, and West Scotland, 
becoming by the refrigeration of the Glacial period those of greatest 
snowfall, were those in which originated the British land ice; and so 
far from this ice being any offshoot from a polar cap, it is probable 
that Greenland was less buried in land ice at that time than it now is, 
because some, and possibly much, of the vapour from the Atlantic 
which now reaches that region, to fall in snow there, must, I infer, 
have then been precipitated in the Atlantic before it could arrive there. 
It has been the land ice to which the extensive phenomena of 
glaciation that arrest the attention of geologists have been almost 
wholly due, while the sea-formed (or floe) ice has, with slight ex- 
ceptions, left its deposits so little marked by evidences of a strikingly 
glacial character, that gravel due to it, though contemporaneous 
with the morainic formation indicative of the land-ice, has been in 
part seized upon to support the hypothesis of interludes of warmer 
climate, and in other part regarded as posterior to that formation. 
Nevertheless the land-ice represents but a small portion of the total 
snowfall, for the greater part of this takes place over the sea, dis- 
appearing directly where this is unfrozen, and where frozen forming 
a cake over the floe ice which eventually disappears in the sea, with- 
out leaving a trace of its existence. Another large part is that 
which falling now on extensive continental tracts, such as are re- 
presented by Siberia, Russia, Scandinavia (save its northernmost 
extremity), the northern parts of the east and centre of the United 
States, Canada, and the Hudson Bay territories up to the very shore 
of the Arctic Ocean, disappears by the summer thaw ; and it is that 
only which from meteorological causes falls in such volume on par- 
ticular places as to exceed the solvent power of the sun there during 
the year which gives rise to land-ice. ‘These places extend many 
degrees of latitude beyond the Polar circles in both hemispheres— 
considerably furthest in the southern, owing to the great extent of 
the maritime area there; and in South Greenland, which is several 
degrees of latitude equatorwards of wide continental expanses where 
there is no land-ice, this ice reaches the sea, and fills and buries 
- channels, and probably straits also, much beneath the sea-level, which 
were it absent would be filled by the sea. 
It is clear that by the Arctic Ocean being frozen over nearly all 
the year, save in that part which is kept more or less,open by the 
Gulf Stream, or its influence, it can in all save that part supply 
but little vapour; and that most of the snow which falls within 
1 Mr. G. M. Dawson indeed, in his paper on the superficial Geology of the Winni- 
peg and Saskatchewan region (Q. J. G. 8. vol. xxxi. p. 620), insists that the features 
of this region conflict with the hypothesis of a polar ice cap. 
