408 PROF. NORDENSKIOLD, expedition to GREENLAND. 



depth of a few inches is soon formed on the skerries and islands 

 in the sea, and serves the sea- fowls as places of incubation. The 

 greatest part of the Greenlander's turf-beds are situated on gulls- 

 hillocks (" maagetuer "), and have, therefore, geologically speak- 

 ing, nothing in common with what we mean by turf-deposits. It 

 was accordingly impossible for me to collect, as I had desired, by 

 an examination of the older turf-beds, materials for determining 

 the latest Post-tertiary changes of climate that have taken place 

 in Greenland. But instead, we find here many other deposits, 

 which serve at least to give an indication of the changes that the 

 animal world has undergone during the Glacial Period. 



Part III. (Geol. Mag., vol, ix., p. 409, &c.) 



Before proceeding to give an account of these changes in the 

 Fauna of Greenland, I wish to draw attention to the possibility 

 which exists in these parts of obtaining a comparison between the 

 units of geological and historical chronology, that is, if, by collect- 

 icg observations and reports from many different localities, it be 

 possible to determine certain limits for the velocity with which 

 the border of the inland ice moves. One may arrive at the lower 

 limit by the following considerations. The breadth of the slip 

 of border-land at Auleitsivikfjord is about 60 miles, or 350,000 ft. 

 The annual retreat can, of course, never exceed the thickness* of 

 the covering that yearly melts, divided by the sine of the inclination 

 of the icy surface, which in the places passed by us was nowhere 

 less than 30°. It is hardly probable that during a summer in 

 Greenland an ice-layer of more than 10 ft. can melt away, so that 

 a yearly retreat exceeding ^^^^30^ = 20 ft. is not to be thouglit of. 

 This would give for the time that has been required for the un- 

 covering of the outer strip of land at Auleitsivikfjord a period of 

 at least 17,000 to 18,000 years. But this number is evidently too 

 low, for neither the yearly falls of snow nor the advance of the 

 ice-mass has been taken into account, as they of course ought to 

 be ; and yet we have here to do with a geological period which 

 undoubtedly forms but a small fraction of the interval that has 

 elapsed since the first appearance of Man. 



The point at Sarpim'sak forms a very level and extensive plain, 

 elevated about 60 to 150 feet above the sea, covered with a vege- 

 tation of "Lyng," Moss, and Sedge, too scanty to conceal the clay 

 which forms the bottom of the plain. Similar formations in many 

 other places along the shores of Disko Bay and Auleitsivikfjord 



* Estimated at right angles to 

 the surface of the ice. The annexed 

 cut shows this more clearly. If G 

 is the surface of the ice in e.g. 1870, 

 and G' the same surface in 1871, 

 then AG' is the thickness of the 

 layer that has melted ; and the 

 distance the ice has receded is = 

 AG': sin V. The angle V is, of 

 course, determined by the relation 

 between the velocity of melting and the velocity with which the ice flows out 

 of the higher parts of the glacier. 



