

A.] FORBES AND RENDU. 531 



(h) Eighth Letter on Glaciers, 1844 (repriu ed 1859, in Occasional 

 Papers, &c., p. 62), I say : ' Facts like this seem to show with evidence, what 

 intelligent men, such as Bishop Reiidu, liad only supposed previously to the 

 first exact measures in IS 1:2, that the ice of glaciers, rigid as it appears, has, 

 in fact, a certain " ductility" or " viscosity " which'permits it to model itself to 

 the ground over which it is forced by gravity,' &c. 



(i) Paper in Philosophical Transactions for 1846 (read 1845 ; reprinted 

 1859, in Occasional Papers, &c., p. 84). 'M. Rendu, Bishop of Anne'c.y, 

 in his excellent Essay on Glaciers, refers in one passage (and I believe in one 

 only) to the possible analogy with a lava stream " [le glacier] s'affaisse-t-il sur 

 lui-meme pour couler le long des pentes comme le i'erait une lave a la fois 

 ductile et iiquide ? " ' l 



(X-) Paper in Phil. Trans. 1846 (Occas. Papers, p. 160). 'Still less 

 could I have anticipated that when the plastic changes of form had been 



:ired and compared, and calculated, and mapped, and confirmed by 

 independent observers, that we should still have had men of science appealing 

 to the fragility of an icicle as an unanswerable argument ! More philosophical, 

 surelv, was the appeal of the Bishop of Annegy, from what we already know 



.iat we may one day learn if willing to be taught. "Quand on agit sur 

 un morceau de glace, qu'on le frappe, on lui trouve une rigidit4 qui est en 

 opposition direct e avec les apparences dont nous venons de parler. Peut- 



ne les experiences faites sur de plus grandes masses donneraient d'autres 

 Hats." ' * 



(/) Thirteenth Lett-er on Glaciers, 1846 (reprinted 1859, Occasional 

 Papers, p. 201). 'Bishop Reudu, whom I had the pleasure of visiting at 

 An nee. y' [in 1846], 'remarked a familiar circumstance which illustrates the 

 same tiling. We often see, in the coldest weather, that opaque snow is con- 



1 into translucent ice by the sliding of boys on its surface ; friction and 

 pressure alone, without the slightest thaw, effect the change which must take 

 place still more readily in a glacier,' &c. 3 



I leave these extracts to the consideration of the impartial 

 reader, that he may decide, by a comparison of them with the 

 extracts in Professor Tyndall's work, or, still better, with 

 Rendu's Essay itself (where, of course, these sagacious views are 

 I with a certain alloy of ingenious but inaccurate conjec- 

 ture) whether they do not constitute an adequate and impartial 

 recognition of the Bishop's TMorie, and at the same time invite 

 and facilitate reference to it. 



1 ' Thiorie des Glaciers. Aftm. de VAcadJmie de Savoie, tome x. p. 93, 



published in 18 H.' 



* ' Theorie des Glaciers de la Savoie, p. 84; quoted in my Travels, p. 367, 

 second edition.' 



I id I been aware of the following passage in Rendu's Theorie, p. 75, 



1 by Professor Tyudall (p. 301), 1 would certainly have cited it : 'D'ofo 



|i>., from an observation by De Saussure on the denies] Ton pent cow-lure (pir 



.pS faYOrisant I'm-lion de 1'aHiiiitr (1< ( '" iii P< iiie lemps la pr. 

 couches les lines SOT les autrcs, rapprochenl les petits enM;m\ (pii Inrnu-nt la 

 neige, ei en les amenant au contact, les i'm parser a IV-i at dc -I.-n-i-.' Nor did 



o his Work \vlim he mad- nk about ' le.-> pctits 



poliasons/ as be called them. (1860.) J 



M M 2 



