A. J FORBES JXD RENDU. 5:29 



(b) Travels, p. 127. ' Ebel gravely affirms 1 that the glaciers of Chamouni 

 advance at the rate of 11 feet a year, and those of Griudelwald 25 feet a-year ; 

 whereas, as we shall see, such spaces are actually traversed by most glaciers in 

 the course of a few days. Tins statement is ouoted by Captain Halls aiK j other 

 recent writers, and even by M. Rendn (uo\v Bishop of Annecy), (he author of 

 a most ingenious paper on glaciers, too little known.'-" 



(c) Tract-!*, p. 188. 'fi, Hendu seems to have been more aware of the 

 importance of the determination of the rate of motion of glaciers than any 

 other author; hut the best information which he could collect in 1841 did not 

 much tend to clear up his doubts. He gives the following rates of motion of 

 the Mer de Glace, or Glacier des Bois, without being able to decide which is 

 the most trustworthy: 212 feet per annum; 412 feet per annum; afoot a 



100 feet per annum ; and 40 feet per annum, or one-tenth of the last ! 

 a difference which he attributes to the different rates of motion of the centre 

 and the sides.' * 



We shall see below (page 16) that Professor Tyndall, in citing 

 ; 'receding passage from my Travels has made two important 

 ions. 



(</) Travels, p. 356. Motto or heading to Chapter XXI. [which is entitled 



ATTEMPT TO EXPLAIN THE LEADING PHENOMENA OF GLACIERS.'] 



-* Rien ne me parait plus clairement demontre que le mouvemeut progressif 



^iers vers le bas de la vallee, et rien en meme temps ne me semble 



plus difficile a concevoir que la maniere doiit s'execute ce mouvement 



silent, si inejral, qui s'execute sur des pentes differentes, sur un sol 



garni d'asperites ct dans des canaux dont la largeur varie a chaque 



L C'est la, scion moi, le phlnomene le moins explicable des glaciers. 



Marche-t -il ensemble comme un bloc de marbre sur un plan incline ? Avance- 



t-il par parties^brisces comme les cadloux qui se suivent dans les couloirs des 



- ? S'affaisse-t-il sur lui-meme pour couler le long des pentes, 



comme le ferait une lave a la fois ductile et liauide ? Les parties qui se 



out vers les pentes rapides sulb'scnt-ellcs a imprimer du mouvement a. 



qui reppsent sur une surface horizontale? Je 1'ignore. Peut-etre encore 



pourrait-on dire que dans les grands froids 1'eau qui remplit les nombreuses 



ransversales du glacier vcnant a sc congelcr, prend son aecroissement 



de volume ordinaire, pousse les parois qui ia contiennent, et produit ainsi 



un mouvement vers le bas du canal d'ecoulement.' RENDU, Theorie de* 







. 367. ' When a glacier passes from a narrow gorge into a 

 initiation to its new circumstances, as a 



viscous substance would do; and when embayed between rocks, it finds its 



through a narrower channel than that by which it entered. This re- 



Xaoier motion, already several times adverted to, had not, 



/lit prominently forward until stated by M. l\eiiuu, now Hishop of 



i ibed it very eleariy in 1h< : " II y a une foule de 



i mbleraient laire eroire fjiie la substance des glaciers jouit d'unc 



lui pcrnirt de se modeler sur la loealite qu''ll<' oeeu])e, de 



mine le ferait nne j.Atr niolle. 



sassises. I utent sansdotite les aniiMs.et 1 



11, nn jour de pluie, IIIH* ehnte de nni:e, un 

 'I. This is e\idently no areoiiMl of the 



/, art. '(i 1 109. 



ItlaSoei'* ' Vc. x. 05. 



M M 



