On the Geological Results of the Polar Expedition. 71 



rapid, its rate having been accelerated by the erection of saw- mills, 

 dams, &c. From the accounts of various travellers who have visited 

 the falls in the last 200 years, the author endeavoured to obtain an 

 estimate of the true rate of recession. Between the visit of Father 

 Hennepin in 1688 and that of Carver in 1766 he finds a recession at 

 the rate of 3-49 feet annually, between Carver's visit and 1856 a mean 

 annual recession of 6*73 feet, and between Hennepin and 1856 one 

 of 5-15 feet. The time-estimates for the cutting of the gorge would 

 be, according to the above means, 12, 103, 6, 276 and 8202 years. 

 The author considers the data upon which the second of these 

 numbers is founded the most reliable. 



April 17. — Henry Clifton Sorby, Esq., F.B.S., President, in the 



Chair. 



The following communications were read : — 



1. "On the Geological results of the Polar Expedition under 

 Admiral Sir George Nares, F.E.S." By Capt. H. W. Feilden, E.A., 

 F.G.S., and C. E. De Eance, Esq., F.G.S. 



The authors describe the Lauren tian gneiss that occupies so large 

 a tract in Canada as extending into the Polar area, and alike 

 underlying the older Palaeozoic rocks of the Parry Archipelago, the 

 Cretaceous and Tertiary plant-bearing beds of Disco Island, and the 

 Oolites and Lias of East Greenland and Spitsbergen. Hewer than 

 the Laurentian, but older than the fossiliferous rocks of Upper 

 Silurian age, are the Cape-Eawson beds, forming the coast-line 

 between Scoresby Bay and Cape Cresswell, in lat. 82° 10' ; these 

 strata arc unfossiliferous slates and grit, dipping at very high 

 angles. 



From the fact that Sir John Eichardson found these ancient rocks 

 in the Hudson's -Bay territory to be directly overlain by limestones, 

 containing corals of the Upper Silurian Xiagara and Onondaga 

 group, Sir Eoderick Murchison inferred that the Polar area was dry 

 land during the whole of the interval of time occupied by the 

 deposition of strata elsewhere between the Laurentian and the 

 Upper Silurian ; and the examination by Mr. Salter, Dr. Haugliton. 

 and others of the specimens brought from the Parry Islands have 

 hitherto been considered to support this view. The specimens of 

 rocks and fossils, more than 2000 in number, brought by the late 

 expedition from Grhmell and Hall Lands have made known 

 to us, with absolute certainty, the occurrence of Lower-Silurian 

 species in rocks underlying the Upper Silurian ; and as several 

 of these Lower -Silurian forms have been noted from the Arctic 

 Archipelago, there can be little doubt that the Lower Silu- 

 rians are there present also. The extensive areas of dolomite of a 

 creamy colour discovered by M'Clintock around the magnetic pole, 

 on the western side of Boothia, in King William's Island, and in 

 Prince -of- Wales Land, abounding in fossils, described by Dr. 

 Haughton, probably represent the whole of the Silurian era and 

 possibly a portion of the Devonian. 



The bases of the Silurians are seen in Xorth Somerset, and 



