John Gunn — Cluwges of Climate. 127 



As these are observations well known to geologists, it is unneces- 

 sary to do more thaa refer to them. 



It may be safely affirmed that there is no part of the world in 

 which, from the continuity and duration of the deposits, the effects 

 of the Precessional movements are more clearly and fully developed 

 than in the County of Norfolk. The consequence of this is that, if 

 the definite extent and number of these deposits could be ascertained, 

 their precise age and duration would also be arrived at, by multipl}"^- 

 ing them by the length of each Precessional cycle ; and if five such 

 can be counted, then the Perihelionic will be completed, amounting to 

 110,000 years. 



In the circumpolar regions the Precessional agency is very power- 

 ful, from the accumulating effects of the greater length of 17|- days 

 of the summer portion of the earth's orbit at either Pole alternately. 

 This is unceasingly going on, adding to and diminishing the store of 

 ice and snow in the Arctic and Antarctic regions by turns. And 

 wherever the more powerful and violent phenomena of the elevatory 

 process of mountain-ranges may be traced, in concurrence with Pre- 

 cession, the result is very gi'eat. 



This is shown in Sir C. Lyell's account of the glaciated condition 

 of Greenland, Student's Manual, p. 147. 



This is so well known that a reference to it also will suffice. 



" Greenland is a vast unexplored continent buried under one con- 

 tinuous and colossal mass of ice that is always moving seaward, 

 a very small part of it in an easterly direction, and all the rest west- 

 ward, or towards Baffin's Bay. All the minor ridges and valleys 

 are levelled and concealed under a general covering of snow, but 

 here and there some steep mountains protrude abruptly from the icy 

 slope, and a few superficial lines of stones or moraines are visible 

 at certain seasons, when no snow has fallen for many months, and 

 when evapoi'ation promoted by the wind and sun has caused much of 

 the upper snow to disappear. The height of this continent is un- 

 known, but it must be very great, as the most elevated lands of the 

 outskirts, which are described as comparatively low, attain altitudes 

 of 4000 to 6000 feet. The icy slope gradually lowers itself towards 

 the outskirts, and then terminates abruptly in a mass about 2000 

 feet in thickness, the great discharge of ice taking place through 

 certain large friths, which at their upper ends are usually about four 

 miles across. Down these friths the ice is protruded, in huge masses, 

 several miles wide, which continue their course grating along the 

 rocky bottom like ordinary glaciers long after they have reached tlie 

 salt water. When at last they arrive at parts of Baffin's Bay deep 

 enough to buoy up ice-bergs from 1000 to 1500 feet in vertical thick- 

 ness, broken masses of them float off, carrying with them on their 

 surface not only fine mud and sand but large stones. These frag- 

 ments of rock are often polished and scored on one or more sides, 

 and as the snow melts they drop down to the bottom of the sea, 

 where large quantities of mud are deposited, and this muddy bottom 

 is inhabited by many molluscs." 



The extent to which the glaciers and icebergs from Greenland 



