December 13, 1901.] 



SCIENCE. 



929 



The literature of the variations of glaciers 

 has been greatly enriched by the contributions 

 of M. Rabot. He has brought together in a 

 convenient form the observations that have 

 been made on the northern glaciers, with refer- 

 ences to his sources of information, so as not 

 only to give an excellent review of what is 

 known of these glaciers, but also to give the 

 data for comparisons with future work. Many 

 of the original publications which he refers to 

 are in languages, such as Icelandic, Danish, 

 Swedish and Norwegian, which are little 

 known outside of the regions where they are 

 spoken, so that his extracts and synopses bring 

 before us important facts which could not be 

 obtained otherwise without great diflSculty. 

 He does not confine himself to the variations 

 of glaciers only, but also gives descriptions, 

 measures of the motion, observations on melt- 

 ing, etc. Although he disclaims that his work 

 is complete, it will be recognized that the in- 

 completeness is not due to oversight on his 

 part, but to paucity of exact information on 

 the subject. One is surprised, indeed, that he 

 has been able to collect so many facts regard- 

 ing more than 250 glaciers, many in very 

 remote regions. 



M. Rabot divides glaciers into three classes : 

 inland ice, such as the ice covering of Green- 

 land with its great ice streams which reach 

 tidewater, including smaller local ice-caps ; 

 Alpine glaciers, with which we are familiar in 

 the Alps ; and composite or Alpine- Norivegian 

 glaciers, an intermediate form grading into 

 each of the other two. Glaciers of the first 

 class are the most common in the arctics. 



In temperate regions, the variations of a 

 glacier are easily determined by the change in 

 the position of its end ; but this is not so simple 

 among arctic glaciers. Many of them end in 

 fiords and the ice is continually breaking off as 

 icebergs, so that the point where they end 

 varies according as we observe them shortly 

 before or after much ice has broken off. M. 

 Rabot thinks the intensity of the calving is a 

 better criterion of the state of the glacier ; if 

 much ice is coming off and at the same time the 

 glacier is not materially receding, it is to be 

 considered in growth ; and vice versa. 



M. Rabot reviews the observations of the 



glaciers of Grinnell Land, Greenland, Jan 

 Mayen's Land, Iceland, Spitzbergen, Francis- 

 Joseph Land and Scandinavia, five of which 

 regions he has himself visited, and brings out 

 many interesting facts, but we can only notice 

 the most important of his conclusions. Of the 

 regions mentioned Iceland and Norway furnish 

 the most detailed information for the longest 

 time. It is well established that the glaciers of 

 these two countries were much smaller before 

 the eighteenth century than they are now, and 

 that this smaller extension lasted for several cen- 

 turies; that there was a great advance during the 

 eighteenth century interrupted for a short time 

 about 1750 ; that during the nineteenth century 

 there has been a slight retreat marked by several 

 minor variations, though the glaciers are still 

 considerably larger than they were during and 

 before the eighteenth century. A Norwegian 

 document of the eighteenth century contains a 

 general description of the Greenland glaciers 

 which might apply to the country to-day, so we 

 must infer that the extent of the ice did not differ 

 very greatly then from what it is now. With 

 the exception of this document all accurate in- 

 formation of the Greenland glaciers refers to the 

 period since 1850. Observations since then are 

 not at all concordant, but they seem to show in 

 general a stationary condition or a slight ad- 

 vance. The natives are unanimous in asserting 

 that the ice has been advancing within his- 

 toric (?) times. The fewer observations in Jan 

 Mayen's Land and Spitzbergen indicate that 

 their glaciers have followed the same history as 

 those of Iceland and Norway. The glaciers of 

 Grinnell Land and Francis-Joseph Land appear 

 to be retreating at present. Local ice caps, 

 probably of comparatively recent origin, cover 

 the islands which make up the latter. 



M. Rabot mentions that the glaciers of south- 

 eastern Alaska seem to have been at a maximum 

 at the end of the eighteenth century ; and it may 

 be added that observations in Glacier Bay show 

 that there was a long period in which the 

 glaciers were much smaller than at present, fol- 

 lowed by the comparatively short but strong 

 advance which apparently culminated at the 

 above date, and that since then there has been 

 a general retreat ; so that it seems quite prob- 

 able that the Alaskan glaciers have experienced 



