288 Scientific Intelligence. 



movement between crust blocks with accumulating strain, the 

 earthquake being the result of a breaking accompanying relief of 

 strain and involving in the sudden movement only a limited zone 

 of strain between two crust blocks. j. b. 



3. La Sismologie moderne (Les tr emblements de Terre) ; par 

 le Comte de 31ontessus de Bailor e y Director of the seismologic 

 Bureau of the Republic of Chili. Pp. 284, pis. and figs. 64. 

 Paris, 1911 (Librairie Armand Colin). — The author of this 

 work is well known as a student of earthquakes, and the purpose 

 which he has had in writing this very readable book is indicated 

 in the preface. Such great catastrophes as that of Messina have 

 awakened a wide interest in earthquakes, but in France no popu- 

 lar w r ork of an authoritative nature has previously met this 

 demand. j. b. 



4. Periodic Variations of Glaciers. — The condition of gla- 

 ciers with reference to stages of advance and retreat has been 

 recorded by the International Commission on Glaciers for the 

 year 1910 (Zeitschrift fiir Gletscherkunde, vi, pp. 81-103, Dec. 

 1911. In the Swiss Alps, of 54 glaciers observed, 16 show actual 

 or probable increase as compared w r ith an average of 10*3 per 

 cent for the years between 1897 and 1909, while only 36 show 

 actual or doubtful decrease, as compared with 55, the average 

 for the ,13 years previous. In the eastern Alps a single glacier on 

 the Wildspitze, reported as advancing in 1909, has been joined by 

 two others; 9 are stationary as compared with two in 1909, while 

 22 out of 34 under observation are known to be retreating. The 

 glaciers about Mt. Blanc considered as a whole show a decrease. 

 The fiva glaciers observed in Sweden have advanced and the 

 measurement of the Norwegian glaciers gives the following 

 results : Jotunheim, 4 advancing, 23 retreating ; Folgefond, 2 

 advancing; Jostedalbrae, S advancing, 6 decreasing; Okstind 

 Mountains, 4 increasing, 2 decreasing. 



In North America the few glaciers reported from the Rockies 

 and the Cascades, also a number north of Juneau and near the 

 headwaters of Copper River, are retreating, while in the Fair- 

 weather range in the Yakutat Bay region and on Copper River 

 the glaciers exhibit an advance. The advance of 9 glaciers in the 

 Yakutat Bay region is believed to be due to accessions from 

 avalanches resulting from the earthquakes of September 1899. 

 The glaciers about Prince William Sound give some indication of. 

 a general but not very large advance. 



This record of glaciers for 1910 needs to be supplemented by 

 reports from other parts ot the world, but the data at hand indi- 

 cates that while there is no general advance yet the decrease in 

 length and mass of existing glaciers which has been continuous 

 for the past two or three decades is not being maintained. 



H. E. G. 



5. Interpretation of Peneplains. — The studies of Mr. E. C. 

 Andrews in the analysis of corrasion and the interpretation of 

 topographic forms carved by water and by ice are important con- 



