540 



SCIENCE 



[N. S. Vol. XLI. No. 1058 



to be admitted for practically all fiord-areas 

 that the valleys are preglacial" (451). "The 

 most fatal objection to the glacial origin of 

 the fiords is the preglacial age of their val- 

 leys" (263). 



It also follows from the glacial theory that 

 the ice streams, being compelled to coincide 

 in direction with the preglacial valleys, must 

 often pursue courses which make large angles 

 with the general direction of ice advance. 

 Yet our author in combating the glacial 

 theory lays much emphasis upon the fact that 

 fiords are not always parallel to the general 

 movement of the ice. " The distribution and 

 arrangement of these Alaskan and British 

 Columbian fiords is quite inconsistent with the 

 theory of their glacial origin. The develop- 

 ment of the fiords appears quite independent 

 of the glaciation of the country; the direction 

 of the fiords is not simply radial from the 

 chief glacial centers" (31Y-18). "The direc- 

 tion of the ice-movement, however, did not 

 fully agree with the trend of the fiords " (140). 

 " Most fiord countries supply abundant in- 

 stances of the fiords and the ice-movements 

 having different directions" (451). 



A still more serious misapprehension is 

 entertained by the author as to the significance 

 of the oft-observed coincidence between fiords 

 and fault lines. As already noted, the glacial 

 theory of fiord origin fully recognizes the fact 

 that the preglacial valleys, later transformed 

 into fiords, were often excavated along ancient 

 fault lines. To prove the presence of a 

 fault-line through a fiord is therefore to prove 

 nothing as to the glacial or tectonic origin of 

 that fiord. But Gregory is not of this opinion. 

 A very large proportion of his argument 

 against the glacial theory consists simply in 

 showing that faults are associated with fiords. 

 Indeed, he is often content to show that some 

 fiords in a region are traversed by faults; or 

 even that faults are known which trend paral- 

 lel with the fiords of a given region; and on 

 such a basis concludes in favor of the tectonic 

 theory of fiord origin. Often he goes so far 

 as to admit that the fiord-valley was not 

 formed by crustal deformation, but by stream 

 erosion along a crushed or weak rock zone; 



yet he cites even such cases in support of the 

 tectonic theory, entirely ignoring the all-im- 

 portant distinction between valleys produced 

 by erosion along ancient fault lines, and de- 

 pressions due to defojrmation along recent 

 fault lines. The fiords of western Iceland are 

 described as " connected with a series of frac- 

 tures " (141) while " Faults are numerous 

 around the Greenland coast, and in many cases 

 they coincide with the fiords" (265). "The 

 evidence for these faults (in Alaska) is often 

 obscured, and along the fiords such faults 

 could hardly be recognized; but their recogni- 

 tion by Messrs. Mofiit and Capps in the Nizina 

 district renders it probable that intersecting 

 faults may be widely distributed through 

 Alaska, and form planes of weakness along 

 which the fiords have been excavated" (322- 

 23). "The tectonic origin of the (New Zea- 

 land) fiords has been recently advocated by 

 Speight. He accepts Andrews' view that they 

 are old river valleys modified by glaciation, 

 but he recognizes that the original course of 

 the valleys was dependent on lines of fracture 

 in the earth's crust" (365). The most pro- 

 nounced glacialist would accept much of 

 Gregory's lengthy argument against the gla- 

 cial theory, as a statement of conditions nor- 

 mally to be expected on the basis of that 

 theory. 



A careful study of the author's ideas con- 

 cerning tectonic valleys in the hope of find- 

 ing some explanation for the apparent lack of 

 consistency in his arguments, only increases 

 one's perplexity. On page 394 we read: 

 " Some valley systems are due to the folding 

 of the earth's crust, which has raised soft 

 bands to the surface, where they are worn 

 into valleys, while the harder rocks resist and 

 remain as ridges. The faulting of the earth's 

 crust also produces bands of weak and shat- 

 tered rocks which are easily washed away, and 

 thus many valleys have been worn out along 

 fault lines. Joints have a somewhat similar 

 effect. . . . Such valleys, though their direc- 

 tions have been determined by earth movements, 

 are valleys of excavation. Tectonic valleys, 

 on the other hand, are the direct results of the 

 earth-movements themselves." This is a clear 



