228 Revieics — W. Uphaui's Lake Agassiz. 



the Coclvington Sandstones, are now placed alongside the Chudleigh 

 Limestone and the Frasnian Beds. The Morte Slates are left in 

 a doubtful position between Upper and Middle Devonian. 



The facts brought forward have reference mainly to the dis- 

 tribution of the several divisions and to the faults and flexures to 

 which they have been subjected; and they are illustrated by an 

 excellent coloured geological map. 



The author gives an interesting account of his discoveries of 

 fossils in the Lower Devonian rocks of South Devon, and hopes that 

 geologists will be stirred up to look for organic remains in the 

 great Grit-beds of North Devon. The Hangman Grits have yielded 

 Natica and Myalina : in the Foreland Grits no fossils have yet 

 been detected. The Morte Slates, regarded as unfossiliferous, have 

 since yielded a Linguln to Dr. Hicks, so that there is hope for 

 those who will have the patience to spend hours on rocks that 

 are apparently barren, instead of devoting their energies to more 

 tempting strata that are known to be fossil iferous. H. B. W. 



VL — Eepokt of Exploration of the Glacial Lake Agassiz in 

 Manitoba. By Warken Upham. Ann. Kept. Geol. and Nat. 

 Hist. Surv. Canada, Vol. IV. Part E. Pp. 156, 2 Maps, and 

 Plate of Sections. (Montreal, 1890.) 



THE suggestion by the late Prof. J. Carvill Lewis that the 

 Boulder-clay of our Eastern counties was formed in a great 

 glacier lake reminded English geologists of the wide extension of 

 such deposits in America. The theory was not a new one in 

 English geology, as it had been used by Agassiz in 1842 to explain 

 the origin of the Parallel Eoads of Glen Eoy, and has been applied 

 quite recently by Goodchild to the high-level drifts of the Thames 

 Estuary. Mr. Warren Upham, in the above Memoir, has now 

 worked out in detail the evidence for the former existence of a 

 glacier lake in Minnesota and Manitoba compared with which our 

 own sink into insignificance. General Wan-en, in 1867, discovered 

 that Lake Winnipeg once had a southern outlet, due, he con- 

 sidered, to an alteration in the contour of the country ; this view 

 was accepted by Dr. G. M. Dawson and Prof. Dana. Prof Winchell, 

 however, in 1877, attributed it to the accumulation of water in front 

 of the northern ice-sheet, and two years later Mr. Warren Upham 

 advocated the same theory, and suggested the name of " Lake 

 Agassiz." According to this view, by the recession of the ice-sheet, 

 a number of rivers were enabled to return to their original northerly 

 direction, but as their waters were dammed back by the ice, a series 

 of lakes were formed, the largest being Lake Agassiz. At first the 

 only outlet of this lake was down the Minnesota Eiver to the south, 

 this being the lowest point on the watershed, but as the glacier 

 receded still further to the north, a series of outlets to Hudson Bay 

 were gradually opened. Five beaches were deposited during the 

 former period, and eleven during the latter. The deposits of the 

 lake now cover 110,000 square miles, so that it was larger than the 

 combined areas of the five Laurentian lakes ; but it never reached 

 this size at any one time ; when the highest beaches of the southern 



