April 9, 1915] 



SCIENCE 



539 



new interpretations, a brief summary may give 

 a fair conception of the nature of the work. 

 When an author of no standing advocates un- 

 usual or startling interpretations, a very short 

 review may suffice to characterize his effort. 

 But when a writer of good standing, profiting 

 by personal observations over an extended 

 field, decides to support in an elaborate treatise 

 a theory rejected as untenable by most of his 

 colleagues in the science, something more than 

 passing notice is required. " The Nature and 

 Origin of Fiords " is the most elaborate work 

 on this subject which the reviewer can recall. 

 In it the well-known author of " The Great 

 Rift Valley" supports a theory which the re- 

 viewer in common with most students of land- 

 forms regards as untenable. The reasons for 

 not accepting Gregory's arguments and con- 

 elusions should therefore be made plain. 



Gregory's book was written primarily to dis- 

 prove the glacial theory and to establish the 

 validity of the tectonic theory of fiord origin. 

 One might anticipate, therefore, that the 

 author would set forth in the clearest terms 

 the essential points of each theory, and more 

 especially the critically important points of 

 contrast between the two. Only after such 

 an analysis would the reader be adequately 

 prepared to weigh the evidence for and against 

 the theories, .and to decide intelligently be- 

 tween them. Unfortunately, while Gregory dis- 

 cusses both theories repeatedly, he presents no 

 adequate analysis of either; and only after the 

 reader has followed with increasing perplexity 

 through a maze of contradictory arguments 

 does he finally discover that the author's con- 

 ceptions as to what are implied by the glacial 

 and tectonic theories often differ radically 

 from the generally accepted views. In order 

 that we may properly appreciate the author's 

 treatment of this important matter, let us 

 summarize hastily some of the essential ele- 

 ments of each theory. 



According to the glacial theory, fiords are 

 partially submerged glacial troughs. The 

 troughs of glaciated mountains far from the 

 sea are similar to fiords, except that the 

 (former have not been drowned by marine 

 waters. In both eases the troughs were formed 



by extensive glacial over-deepening of former 

 river valleys. The preglacial valleys guided 

 the glaciers which later came to occupy them, 

 and by confining the ice streams to the narrow 

 limits imposed by the valley walls insured 

 a maximum efficiency of glacial erosion. The 

 glacial theory asks no questions as to what de- 

 termined the courses of the preglacial valleys ; 

 but it is fully recognized that among other 

 causes ancient fault lines must be considered, 

 since a fault may give a crushed zone which 

 is weaker than the unfractured rock, or may 

 bring a belt of weak rock into such position 

 that subsequent valleys will soon be excavated 

 along it, and hence parallel to the fault. 



According to the tectonic theory, on the 

 other hand, fiords are directly due to forces 

 within the earth which cause a pronounced 

 local and recent deformation of the earth's 

 surface. This deformation may be in the 

 nature of a gaping fissure where the rocks 

 have parted along a fault or joint plane; or 

 it may consist of a rift valley or graben caused 

 by the down-dropping of a narrow strip of the 

 earth's crust between two parallel faults. 

 Such depressions may later be modified by 

 river or glacial action; but the essential fea- 

 tures of fiord topography must have existed 

 prior to such modification. And whereas, ac- 

 cording to the glacial theory, many fiords may 

 be located along fault lines or joints, accord- 

 ing to the tectonic theory every fiord must be 

 so located. 



Without pursuing this contrast further, let 

 us turn again to Gregory's treatment of the 

 problem. His misconceptions of the glacial 

 theory are at once apparent. We have seen 

 that this theory involves the recognition of 

 preglacial river valleys which determined the 

 courses of the more recent ice streams. Yet 

 Gregory devotes a large amount of space to 

 arguing that the valleys existed before the ice 

 came, under the erroneous impression that 

 this is incompatible with the glacial theory. 

 In chapter after chapter this remarkable posi- 

 tion is vigorously maintained. Indeed, he 

 teUs us that " The most conclusive argument 

 against the glacial origin of the fiords is the 

 preglacial age of their valleys; and it appears 



