APH1L33, 1897.] 



SCIENCE. 



661 



latter, of course, claim the greatest attention, 

 on account of their number, size and vai-iety. 

 Here are the most accessible tide-water glaciers, 

 and many tourists have already seen the birth 

 of icebergs at the end of Muir glacier. Here 

 also is the great Malaspina glacier, a mass of 

 ice formed by the coalescence of the ends of 

 many glaciers descending from the St. Elias 

 Alps. It lies on a flat expanse between the 

 mountains and the ocean and covers an area of 

 some 1,500 square miles. Professor Eussell 

 has crossed this glacier along several lines and 

 practically all we know of it is due to his ex- 

 plorations. It is the only Piedmont glacier that 

 has been visited. 



The absence of glaciers in the central and 

 northern parts of Alaska is explained as due to 

 insufficient precipitation ; but in these regions 

 we find the strange subsoil ice whose thickness 

 has not been determined, but which in places 

 certainly extends several hundred feet below 

 the surface of the soil. 



The glaciers in the northeastern part of the 

 continent occur both in Grinnell Land and 

 Greenland. Some of the former have been vis- 

 ited and described, but have not received much 

 attention, whereas the latter have attracted 

 quite a number of observers. The recent stud- 

 ies of Professor Chamberlin first made us 

 familiar with certain remarkable characteristics 

 of these glaciers which are not found in regions 

 further south. 



In the chapter on Climatic Changes, Professor 

 Russell shows that the glaciers of North Amer- 

 ica, with a few exceptions, are growing smaller; 

 and he mentions the eflfbrts being made by the 

 International Committee on Glaciers to collect 

 information on the variations of glaciers every- 

 where. 



In telling of ' How and Why Glaciers move,' 

 the observations of Kock and Klocke are nar- 

 rated. These observers thought they had de- 

 tected certain irregularities in the motion of the 

 Moteratsch glacier, parts of the ice moving at 

 times up the valley. Professor Russell is cau- 

 tious in accepting such an anomaly, and indeed 

 the observers themselves have since recognized 

 that these irregularities were within the limit 

 of the errors of observation. 

 . The hypotheses which have been advanced 



to account for the apparent plastic flow of ice, 

 notwithstanding its great brittleness, are well 

 given and well criticised, especially from the 

 point of view of the geographer ; though James 

 Thomson's theory is too shortly dismissed, and 

 CroU's hypothesis receives more attention than 

 it deserves, for it is radically wrong. The 

 growth of the glacier grains, as a cause of 

 motion, has been advanced from time to time, 

 but has not been sustained ; Forel developed 

 this hypothesis into a theory, but found later 

 that it was not supported by his observations. 



Professor Russell believes that the motion of 

 glaciers is due principally to the plastic flow of 

 ice under its own weight, but that many other 

 causes play a minor part; some of these a physi- 

 cist would throw out entirely. 



The book closes with a very interesting chap- 

 ter on 'The Life History of a Glacier.' This 

 is an extension of Professor Davis' topographical 

 cycle to the history of a glacier, and is an 

 entirely new addition to glacial literature. 



A slip is made on page 181 in saying that the 

 heat absorbed when ice melts equals the heat 

 necessary to raise the water thus formed from 

 its freezing to its boiling point, and §11, p. 187 

 is misleading ; exception might also be taken 

 to the statement (p. 192) that in a vertical sec- 

 tion through the n6ve-fields the maximum flow 

 [velocity] would probably be near the bottom. 



This book may be heartily commended to the 

 general reader, and will be of great help to the 

 student of glaciers. It is illustrated by a num- 

 ber of well-selected pictures and maps, and 

 important references are given in foot-notes. 

 Haeey Fielding Reid. 



Geological Laboratory, 

 Johns Hopkins University. 



Neudrucke von Schriften und Karten iiber Meteor- 

 ologie und Erdmagnetismus, herausgegeben von 

 Peof. De. G. Hellmann. 



No. 7. Esperienza dell' Argento Vivo. EvAN- 

 gelista Toeeicelli. Istrumenti per conos- 

 cer P Alterazioni dell' Aria. Accademia del 

 CiMENTO. 4to. Pp. 22, 16. 



No. 8. Meteorologische Karten. E. Halley, A. 

 VON Humboldt, E. Loomis, U. J. Le Vee- 

 EIEE, E. Renou. 1688, 1817, 1846, 1863, 

 1864. 4to. Pp. 13. Charts 6. 



