Apkil 9, 1915] 



SCIENCE 



541 



statement of the generally accepted distinc- 

 tion between erosion valleys guided by struc- 

 ture, and tectonic valleys; but it is directly 

 contradicted by the major portion of the au- 

 thor's arguments on the preceding 300 pages 

 of the book. The contradiction is even more 

 amazing when we compare this statement with 

 one on page 455, where tectonic valleys are 

 divided into several groups and one group is 

 defined as follows : " Valleys formed along 

 fault-planes owing to the removal by denuda- 

 tion of a belt of rocks which has been crushed 

 by earth-movements." It is clear that the 

 author's ideas as to what constitutes a tectonic 

 valley, the most vital point in his entire book, 

 were confused and contradictory, and varied 

 from time to time as he wrote. Similar con- 

 tradictions regarding other matters appear 

 so frequently throughout the book that it is 

 often quite impossible to know what opinion 

 the author really holds regarding essential 

 points in the problem he discusses. 



Throughout the book much reliance is 

 placed on authority, and hundreds of quota- 

 tions favorable to the tectonic theory are ad- 

 duced to strengthen the case for that theory. 

 Many of these quotations date back to a time 

 when the knowledge of land forms was in its 

 infancy; others are from writers unqualified 

 to speak authoritatively on the interpretation 

 of land forms; and occasionally the author 

 quoted wrote in a poetic or figurative sense. 

 In the chapter on Alaskan fiords Gregory 

 writes : " The explanation of these fiords as 

 simply due to glacier corrosion seems to me 

 quite inadequate. That they are due to the 

 action of some tectonic force has been recog- 

 nized by many visitors to them. Mr. John 

 Burroughs has graphically expressed this 

 view." Then follows this quotation from Mr. 

 Burroughs : " The edge of this part of the 

 continent for a thousand miles has been 

 broken into fragments, small and great, as by 

 the stroke of some earth-cracking hammer, 

 and into the openings and channels thus 

 formed the sea flows freely, often at a depth 

 of from one to two thousand feet." The fact 

 that Mr. Burroughs is not a geologist, and is 

 therefore presumably unacquainted with 



Alaskan geology, did not deter Gregory from 

 citing this bit of imagery as a substantial 

 confirmation of his theory. Views unfavor- 

 able to the tectonic theory are also quoted at 

 length, but are quickly dismissed as unten- 

 able. Favorable views are as quickly ac- 

 cepted. In neither case is there any serious 

 attempt to present the quoted author's evi- 

 dence, review his line of argument, and then 

 subject his conclusions to critical analysis 

 before accepting or rejecting them. 



Another reason for accepting Gregory's 

 work with reserve is found in his frequent 

 misinterpretation of the views entertained by 

 authors from whom he quotes. His own be- 

 lief in the tectonic theory was so strong that 

 he unconsciously read into the works of others 

 ideas favorable to his theory which they did 

 not express. Of the many instances of this I 

 will cite but a few. On page 309 Gregory re- 

 fers to the work of Tarr and Martin on the 

 Yakutat Bay earthquake, and while he ac- 

 knowledges that these authors recognized but 

 one fault along Eussell fiord, and attributed 

 the present depth and form of the fiords to 

 glacial erosion, he goes on to say that "the 

 shores of this fiord appear to lie along two old 

 faults, the prolongation of which formed the 

 valley occupied by the Hidden Glacier, and 

 movements along the two faults would ex- 

 plain the facts as well as along one fault. 

 This earthquake illustrates how fiord valleys 

 have been formed by parallel trough-faults. 

 . . . Tarr and Martin's memoir shows that 

 the formation of fiord-valleys by trough fault- 

 ing is still in progress in Alaska." After 

 reading this, one unfamiliar with the memoir 

 in question will be surprised to find that Tarr 

 and Martin considered the faulting hypothe- 

 sis of origin for these fiords at length, ad- 

 duced a variety of evidence opposed to this 

 theory, and concluded by showing that it was 

 quite impossible to explain the fiords as a 

 product of faulting. According to Martin 

 the stratigraphic evidence positively proves 

 the absence of two parallel faults. In sup- 

 port of his position Gregory says that in a 

 later memoir Tarr " attached less importance 

 to glacial action'" in the formation of fiords. 



