THE GEOLOGY OF THE AECTIC COASTS. 567 



The accounts given of trees having been found in similar Post- 

 pliocene beds in the Polar regions, under circumstances that would 

 lead to the supposition that such trees had grown in situ, are not to 

 be relied on y and no evidences were discovered in the mud-beds of 

 Grinnell Land to encourage the opinion that there have been any 

 interglacial periods of increased temperature, at all events during 

 the long time which must have elapsed while Grinnell Land was 

 rising to an altitude of 1000 feet above the present sea-level. 



Dr. R. W. Coppinger, who accompanied Lieut. Fulford in his ex- 

 ploration of Petermann Fiord in May and June 1876, after leaving 

 Offley Island some fifteen miles, found the fiord to be bounded by 

 vertical cliffs 1100 feet high, composed of alternating bands of light 

 grey and dark slate -coloured fossiliferous limestone rock, surmounted 

 by an ice-cap, with a blue jagged edge lying flush with the face of 

 cliffs, which was estimated to be 40 feet in thickness. A similar ice-cap 

 prevailed on the south-west side ; and on both sides the ice appeared 

 to be flowing steadily over the cliffs, as evidenced "by frequent 

 avalanches, in which great masses of the ice-cap projecting over the 

 cliffs become detached, and carrying with them in their descent 

 masses of rock torn from the face of the cliffs," sometimes projected 

 on to the floe a distance of 80 yards. 



The surface of the ice of the floe is traversed by north and south 

 ridges running obliquely down the fiord for a distance of sometimes 

 two miles, though usually interrupted by wide fissures and faults, 

 which become more numerous as the glaciers are approached. These 

 form nuclei of disruption of the main ice. At certain states of the tide 

 the glacier-ice appeared to be aground, and at others to behave as floe- 

 ice. The depth of the furrows on the floe, measured from crest to 

 trough, was often 30 feet, and the sides exceedingly slippery and 

 difficult to travel on, and the glacier-ice was equally formidable ; 

 but enough was seen to render it certain that the fiord had been 

 occupied by an immense glacier, which has retreated to its present 

 dimensions, and whose main course lay to the east, the small 

 glaciers flowing through the cliffs adding little to the volume of 

 ice, which is affected by tidal action for more than a mile above 

 the mouth. 



The whole of Offley Island is traversed by glacial planings, 

 scorings, and groovings, from its summit at the north-east, down to 

 the beach at the south-west end, the rock consisting of fossiliferous 

 black and grey limestone. 



A very noticeable feature of Grinnell Land is the paucity of gla- 

 ciers and the non-existence of an ice-cap, such as prevails in North 

 Greenland. In Grinnell Land, north of latitude 81°, no glaciers 

 descend to the sea-level, which they do in the same parallel on the 

 opposite or Greenland coast of Hall Basin*. 



EXPLANATION OF PLATE XXIV. 



Sketch Map showing the Geology of Grinnell Land and the neighbouring 

 regions. 



* For the Discussion on this paper, see p. 636 



