May 14, 1897.] 



SCIENCE. 



751 



The author recognizes that the conclu- 

 sions of Chamberlin and Salisbury are 

 based upon evidence of two kinds : " one, 

 the presence of a driftless area in the In- 

 glefield Gulf region, announced by Profes- 

 sor Chamberlin ; and a second, the angular 

 topography of the Greenland coast, de- 

 scribed by both." The first evidence, al- 

 though vital to a general conclusion, is passed 

 without discussion, because it was not seen 

 by the author. He remarks, however, in a 

 footnote that he " cannot let this opportu- 

 nity pass without raising the query whether 

 the topography in the neighborhood of the 

 Greenland driftless area is not such that an 

 area of this sort would naturally be ex- 

 pected. "Was not the movement of the ice 

 outward and the main stream down the In- 

 glefield Gulf? And is not the driftless area 

 located in the place where the high Red 

 Cliff peninsula would naturally have clogged 

 the ice and hence prevented its action of 

 erosion and notable transportation ?" The 

 driftless area is a part of the same ancient 

 peneplain as the summit of the Red Cliff 

 peninsula {Journal of Geology, p. 205-6, Vol. 

 III., 1895). It lies on the east side of Red 

 Cliff peninsula (see map, p. 668, Vol. II., 

 Jour. Geol.). Tt\\QS between it and the great 

 ice cap. It is separated from the peninsula 

 by the valley of Bowdoin bay, about two 

 miles wide and 2,000 feet deep. How an 

 isolated part of a peneplain can protect 

 from glaciation another part of the same 

 plain lying between it and the source of the 

 glacial motion and several miles distant is 

 not easily understood. The suggestion ap- 

 parently sprang from the same lack of cir- 

 cumspection that gave birth to the main is- 

 sue without adequate grounds. 



The evidence drawn from topography is 

 the main subject of discussion in the initial 

 portion of the paper. The essential point 

 urged in the paper and reiterated in subse- 

 quent discussion is that angularity of to- 

 pography is compatible with general glacia- 



tion, and that general observations on to- 

 pographic contours have little or no value 

 in deciding the prevalence of glaciation. 

 The most important illustrative evidence 

 in support of this is a photographic view of 

 ' The Devil's Thumb.' The photograph is 

 here reproduced (PL 26, Vol. VIII., 1886, 

 Bull. Geol. Soc. Am.) . (Fig. 1.) Nothing has 

 recently so astonished the present writer or 

 his colleague as the presentation of this 

 photograph as an illustration of the absence 

 of topographic signs of glaciation. It is a 

 marvel to us how any glacialist could fail 

 to read from these contours — even from the 

 summit contours — just that degree of gla- 

 ciation which was found by the more rigor- 

 ous lines of study. It is true that the lee 

 side is angular, but this does not in any es- 

 sential way confuse or obscure the dominant 

 expression, which is that of moderate gla- 

 ciation. That geologists may see how dif- 

 ferent are the contours that led Professor 

 Salisbury and the writer to infer absence of 

 glaciation in certain other regions, there is 

 here reproduced the photograph of Dal- 

 rymple Island which was used as an illus- 

 tration of the asperities of a typical angular 

 topography {Jour, of Geol., Vol. II., p. 661). 

 (Fig. 2.) It must be evident to the critical 

 observer that the two topographies belong to 

 distinct types. The contours of Dairy mple 

 Island clearly show the absence of any gla- 

 cial softening. The contours of the so-called 

 Devil's Thumb and of the adjacent region 

 clearly portray a moderate measure of gla- 

 cial softening. The normal asperities of a 

 non-glacial arctic topography are gone. 

 This topographic expression seems to the 

 reviewer to be such as to be read with ease 

 and accuracy even at a distance, especially 

 after the general habit of the region has 

 been determined by more rigorous lines of 

 evidence. The photograph does not sus- 

 tain the author in calling the topography 

 angular in an unqualified sense ; nor does 

 it sustain him in insisting that it is imprac- 



