448 



NATURE 



{Aprils, 1875 



inland district, where not one trace of life, one patch of 

 earth, or one single stone occurs to enliven the monotony 

 of a silent and to the eye motionless ocean, extending for 

 1,200 miles from north to south, with a breadth of 400 

 miles. When the additional matter of eight months' 

 snow is poured upon it the glacier overflows, finding a 

 way through the fjords, the overflow corresponding to the 

 effluent glaciers, some of which, like the Humboldt 

 Glacier in Smith's Sound, are sixty miles in width. 

 Where no fjords are available, the ice pours over the 

 cliffs, hanging until gravity overcomes its cohesiveness. 



Dr. Rink believes that the outpour of the Greenland 

 precipitation of snow and rain in the form of glacier ice 

 amounts to only two inches, while he estimates the fall at 

 twelve inches ; so that, as the evaporation must be exceed- 

 ingly small, a large portion of the remaining ten inches must 

 be carried off by sub-glacial rivers : Dr. Rink instances a 



lake which rises whenever the glacier river disappears. The 

 effect of these streams on the moraine pro/onde, or couche 

 de bone, as Agassiz called it, the result of the trituration 

 of the rocks over which the ice passed, must be consider- 

 able, and accounts for the muddy water found opposite 

 the entrance of all ice fjords, and the eventual choking 

 up of the channels through which the bergs, broken off 

 from the face of the " lis-blink " (ice-glance) of the Danes, 

 plough their way on their journey seawards, the direction 

 of which is entirely governed by that of the currents, and 

 not invariably, as often imagined, from the north to the 

 south. 



Ground-ice has been shown by Dr. Henry Landor 

 to form in Canadian streams, when the thermometer is 

 at zero, being most abundant where there is no surface- 

 ice ; as it gradually thickens, it becomes honey-combed 

 in the direction of the current, the water flowing through 



the tubes. In course of time it floats, bearing up the 

 stones to which it is anchored, often of large size, descends 

 the stream, and becomes frozen up in the surface-ice. 

 The movement of these ice-floated boulders often pro- 

 duces grooves on the faces of cliffs, as well-marked, ac- 

 cording to Sir W. Logan, as those of glacial times. 



Ground-ice laden with sea-weed, stones, and gravel, 

 often rises in the shallow portions of the Baltic, where 

 sheets of boulder-laden ice are driven by storms, and 

 packed on the coast to a height of 50 feet. In Davis 

 Straits the sea-water has a specific gravity, according to 

 Scoresby, of I '0263, and freezes at 28-0° F., when the salt, 

 5f oz. to the gallon, is precipitated, and the "bay-ice" of 

 the whalers is formed, which eventually becomes a floe, 

 and afterwards pack-ice. The ice, in summer, melts 

 on the sides of the channel before that in the centre, 

 which constitutes the middle ice of the whalers ; but 

 between the open water and the land a narrow fringe of 

 ice still hangs to the chff, the "iis-fod" of the Greenland 



Danes. This, receiving large quantities of land-slips and 

 other debris from the cliffs, afterwards breaks up and 

 floats seawards, grazing the rocks at low tide, and on 

 melting, deposits the fragments at the bottom of the sea ; 

 thus forming a close analogy to those conditions which pre- 

 vailed when the English boulder-clay was deposited, 

 beneath which the rocks are smoothed and scored, iii 

 positions that render it improbable that it was done by 

 glacier ice ; the latter prevailed, however, in Britain both 

 before and after the period of submergence. The occasional 

 patches and nests of sand and gravel found in boulder- 

 clay may well have been derived from portions of the gravel- 

 laden ice-foot which became entangled in the pack-ice. 

 Masses of ddbris-laden ice-foot derived from one district 

 are often driven by winds and high tides on to the coasts 

 of other districts, which well explains the lines of more or 

 less rounded tumultuous gravels found in many parts of 

 Britain. 

 Kane's and Hayes' expeditions found distinct terraces 



