NATURE 



21'J 



THURSDAY, JULY 7, 1904. 



THE HARRIMAN ALASKA EXPEDITION. 

 Alaska. Vol. iii.— Glaciers and Glaciation. By 

 G. K. Gilbert. Pp. 231; 18 plates and 106 text 

 fifjures. Vol. iv.— Geoloev and Palaeontology. By 

 B. K. Emerson, C. Palache, W. H. Dall, E. O. 

 Ulrich and F. H. Knowlton. Pp. 173; 32 plates and 

 18 text figures. (New York : Doubleday, Page and 

 Co., 1904.) 



IT is now nearly two years since we noticed in our 

 pages (Nature, vol. Ixvi. p. 176) the two hand- 

 some volumes which were the first-fruits of the scien- 

 tific holiday cruise in Alaska carried out in the summer 

 of iSgq by a party of competent observers through the 

 liberality of Mr. E. H. Harriman. Two further 

 volumes of the series are now before us, one recording 

 the observations made on glaciers and glaciation 

 during the expedition, and the other dealing with the 

 geology and paleontology of the places visited. 

 Though necessarily of more restricted interest than the 

 two first volumes, which dealt with general and varied 

 topics, these books are scarcely one whit behind their 

 predecessors as specimens of the printer's art, except 

 in the matter of coloured plates. Profusely illustrated, 

 well printed on good paper, and tastefully bound, it is 

 evident that no expense has been spared in their pro- 

 duction, and rarely do we find technical writings be- 

 decked in such garb. The toned plates are beautifully 

 reproduced, but the line drawings from photographs, 

 which constitute most of the text figures, appear to 

 have suffered to a certain extent from the very 

 excellence of the paper, and would probably have shown 

 to better advantage on the heavy smooth-surfaced pro- 

 duct that we growl over so often in American books. 



Neither volume is monographic for its subject, but 

 while giving many references to previous literature and 

 to data accumulated by foregoing explorers, deals 

 mainly with the direct results of the expedition. In 

 fact, the books are essentially a series of " papers " on 

 the geology of Alaska, and the subject-matter is 

 treated accordingly. 



The first of these volumes (vol. iii. of the series) 

 consists of observations on the glaciers visited by the 

 party, and on the general glacial phenomena of the 

 region, Mr. G. K. Gilbert acting as recorder in this 

 subject. In his lucid descriptions of the existing 

 glaciers and in his able discussion of some of the 

 problems connected with their past history, Mr. Gilbert 

 presents much that is of extreme interest to the 

 glacialist, though the opportunities for personal study 

 were mainly confined to the lower ends of glaciers that 

 reach nearly or quite to tidal waters. In all cases, 

 care is taken to give details and illustrations from dated 

 photographs, so that future observers will be enabled 

 to determine the movement of the ice-front. In 

 many instances, past records were in existence which 

 permit the modern changes in the length of the ice- 

 rivers to be discussed. Curious discrepancies between 

 the conditions in different parts of the country are 

 recognised, for while some glaciers are in rapid re- 

 NO. I 8 10, VOL. 70] 



treat — e.g. the Muir, which when visited in 1899 was 

 more than a mile and a half shorter than it was nine- 

 teen years previously- — others had recently advanced. 



" The most conspicuous fact brought out by the com- 

 parison of local histories is that they are dissimilar. 

 Nevertheless, there are limited resemblances. The 

 Glacier Bay and Disenchantment Bay histories agree 

 in including a great retreat, occupying more than a 

 century. The Port Wells and Grewingk histories 

 agree in a moderate retreat occupying something less 

 than a century. The La Perouse and Columbia 

 histories agree in a present condition of maximum 

 glaciation probably preceded by an important mini- 

 mum " (p. 104). 



The possible cause of these variations is discussed ; 

 and although no definite conclusion is reached, it is 

 suggested " that the combination of a climatic change 

 of a general character with local conditions of a varied 

 character, may result in local glacier variations which 

 are not only unequal but opposite " (p. 109). 



The Columbia and La Perouse glaciers in their 

 recent advance have invaded a mature forest-growth 

 which had established itself near their margins. Most 

 instructive to the glacial geologist are the illustrations 

 and descriptions of the " push-moraines " of bouldery 

 till full of crushed trees — in one case " not only tree 

 trunks and branches but folds of peaty soil " (p. 77) — 

 which, by a slight recent retreat of the ice, are left 

 open to investigation along the devastated fringe of 

 the forest. In looking at these pictures one might 

 imagine that some gigantic wild boar had been uproot- 

 ing the ground. Noteworthy, too, are the stream-built 

 " waste plains " of coarse gravel which overspread the 

 valley-floor in cases where the glacier does not reach 

 quite to the sea, as described and illustrated in the in- 

 stances of Hidden Glacier (p. 53) and Grewingk Glacier 



(P- 94)- 



It is mentioned that in 1899, soon after the visit of 

 the expedition. Glacier Bay was choked up with floating 

 ice, apparently due to the disintegration of the tidal ice- 

 fronts by an earthquake shock. And since then, until 

 the time of writing, it had been impossible for steamers 

 to approach within several miles of the Muir Glacier. 



The effect of ice-falls from the ends of tidal glaciers 

 was observed to produce waves sufficient to erode the 

 coast in places where wind-waves could not form ; and 

 it is suggested by Mr. Gilbert that we may thus explain 

 the clear outlining of the shores of some glacial lakes 

 the area of which seems to have been insufficient to pro- 

 duce important wind-waves. 



In dealing with the Pleistocene glaciation (chapter 

 ii.), Mr. Gilbert discusses the origin of the " hanging 

 valleys " so abundant in this region, and accepts the 

 view that the discordance of level between the trunk 

 and tributary valley is in most cases due to the deeper 

 glacial excavation of the main trough. 



" It [the hanging valley] is a conspicuous earmark 

 of the former presence of glaciers ; and it helps to a 

 conception of the magnitude of Pleistocene glacial 

 erosion " (p. 115). 



The grounds on which this assumption is based are 

 fully stated and illustrated. Great stress is laid upon 



