1848.] ANALOGIES DERIVED FROM LAND-SLIPS. 211 



years ago, I obtained a French work, entitled, " Recherches 

 Experimentales sur les Glissements spontanes des terrains 

 argileux, par Alexandre Collin, Ingenieur des Pouts et Chaus- 

 sees." Paris, 1846, 4to. This interesting work, illustrated by 

 plates, contains no allusion to the subject of glaciers; the pheno- 

 mena of mud-slides being considered solely in an engineering point 

 of view. The principal object of the work is to investigate the 

 form of the surface of sliding, which separates the solid from the 

 moving soil of railway cuttings, embankments, and the like. 

 That subject is not particularly connected with the one before us ; 

 but M. Collin has, at the same time, presented us with excel- 

 lent and detailed sections of land-slips, the mere inspection of 

 which recalls forcibly the outline of glaciers, and, although evi- 

 dently unaware of my theory of the latter, his remarks confirm, 

 in a very satisfactory way, several of my anticipations respecting 

 the internal movements of viscous bodies. Thus, in the trans- 

 verse section of an embankment of the Paris and Versailles Rail- 

 way (Rive gauche) [copied in Plate IX. fig. 1., of the present 

 volume], we find the original declivity of forced earth, denoted 

 by the dotted line, remodelled by the slide over the surface DFE 

 into the bulged form FGH, which recalls at once the terminal 

 section of a glacier. In fig. 2, again, we have a similar pheno- 

 menon, observed at Cercey in Burgundy, where the mass has been 

 more solid, the swelling of the surface less continuous, and trans- 

 verse crevasses, exactly like those of a glacier, have opened. 

 The length of the talus or declivity, before sliding, was about 

 26 metres, or 85 English feet, in the first case, and 24 metres, 

 or 79 English feet, in the second. M. Collin also measured 

 daily, for more than two months, the horizontal advance of 

 the lower extremity of the earth-slide of Cercey, and likewise 

 the perpendicular fall of its upper extremity. These results, 

 which are the only ones of the kind which 1 have met with, 

 are highly interesting, as shewing the continuity and general 

 regularity of this very small motion in a mass which could not 

 be called fluid, in any ordinary sense of the word, since we 

 are told that there was not the slightest trace of any exudation 



