SIE HENRY H. HOWOETH. P.C.L., f.R.5., OX ICE OE WATEE. 221 



has been obtained witliin ^'erv recent years — perhaps after some 

 of the pages from which I quote were written. 



The Epeirogenie theory in general characters resembles that 

 of Lyell — wliich has been rather slightly touched upon by our 

 author — but it differs therefi'om in this respect, that Lyell's 

 theory is based on the interchange of land and sea, rather 

 than on the vertical uplift of the land. Lyell showed in his 

 grea^ work {Principles of Gcolorpi) that if the great mass 

 of continental land was disposed round the pole — and its 

 present position occupied by the ocean — cjlacial conditions 

 would be the result. Of this tliere can be no doubt ; but 

 there is no evidence that such a distribution of land and 

 water took place in Post-Pliocene times. It was an hypothesis 

 and nothing inore. 



The Epeirogenic theory, on the other hand, is based on actual 

 observation by means of soundings along both sides of the 

 Atlantic and more recently by Xansen in the Polar seas. 

 These observations unc|uestionably prove that the existing 

 river-valleys entering the ocean are prolonged outwards under 

 the surface, and traverse the continental platform in the form 

 of canons, with well-defined sides, to depths of several thousand 

 feet. As such valleys could only have been eroded under the 

 atmosphere, the inference is simple and inevitable, that these 

 areas were in the condition of land when the valleys were in 

 course of formation. 



The credit of working out the form and direction of these 

 "drowned valleys" on the American side is chiefly due to 

 Professor J. "\V. Spencer, whose name scarcely occurs, I regret 

 to say, in the volume now under review ; but undoubtedly it 

 would have added much to the value of this work if there had 

 been a full treatment of the subject regarding the formation of 

 the sub-oceanic physical features. 



As members of the Institute are aware, the writer has 

 contributed several papers descriptive of these submerged 

 valleys on this side of the Atlantic* to the Transactions, and 

 the determination by Dr. Xansen of similar features bordering 

 the Arctic lands (including the continental platform and the 

 valleys by which it is traversed) ought to assist in dissipating 

 the unreasonable prejudice which has retarded the general 

 acceptance of the results at which we have arrived. 



* Vols. XXX, p. 205, XX xi, p. 259, xxxii, p. 147 : and Professor Lfgan 

 Lobley, vol. xxxiii, p. 419. 



