BY E. C. ANDREWS. 797 



streams in order to appreciate the real shock of attack by which 

 the land-contours had been carved. He who would see the true 

 state of affairs must watch the Titan delivering his heaviest blow. 

 Not that the succeeding pigmy-streams are incapable of continu- 

 ing the work started by the giant, but merely that, while yet 

 they are occupied in obliterating the Titan's marks, he again 

 returns and carries on his former work of reduction. 



The clear conception of the fact that shorelines, valley-floors, 

 and fiord-contours result from the action of successive mighty 

 floods, would put to rest many disputed points in glaciation and 

 peneplanation; for it would at once be observed that drought 

 streams slumber peacefully among the wreckage produced by the 

 floods. So enormous were the weapons with which the giant 

 streams armed themselves, and so flat were the grades thev pro- 

 duced, that all the energies of normal streams or glaciers are 

 utilised in merely filling up the holes resulting from such Titanic 

 attack, or in forming lakes to surmount the masses of debris 

 dropped here and there in the bed of the stream, upon the 

 retreat of the great flood. 



So simple was the principle that many Avorkers appear, tacitly, 

 to have admitted it; nevertheless they would not perceive its 

 main significance. To Dr. G. K. Gilbert (17,a pp.89-90) belongs"^ ' 

 the honour of having first, in 1883, clearly enunciated the 

 principle as it applies to ordinary streams and coastlines. Yet 

 even that acute and philosophic geologist hesitated to apply his 

 ownf far-reaching discovery to glacial studies. (17) 



The present paper is an attempt to throw further light on 

 Gilbert's principle by a comparison of observed small effects, such 

 as one sees in storm-gutters, wdth the grand contours obtaining 

 along large streams and glacial channels. 



* Gilbert, G. K. —Quoted at length later (p. 800). The idea had occurred 

 independently to the present writer in 1905. See Andrews, E. C. {postea). 

 Dr. Gilbert's paper was not read by the writer until 1907. 



t Dr. Gilbert in a letter to the writer (August, 1907) states that this idea 

 came independently and contemporaneously to both J. W, Powell and 

 himself. 



