338 TRAVELS A3I0NGST THE GREAT ANDES, chap. xix. 



The latter stand in advance of the higher ones, and are passable 

 at F (''the breach^), or may be skirted at the base. The upper 

 cliffs B, B are unapproachable, on account of being crowned by 

 glacier, which falls at intervals in tremendous avalanches, shaving 

 the face of the rock. This ice -section (E, E), at the top of the 

 cliffs, shews the thickness of the glacier on the summit of 

 Chimborazo. 



The faces of these precipices exhibit a large number of parallel 

 bands (nearly horizontal in the lower series and distorted in the 

 upper one) which are highly coloured, and upon the rare occasions 

 that the cliffs are lighted by the sun they present a gay and 

 attractive appearance. The highest strata of the upper series are 

 black, ^ alternating with grey bands ; warm grey, passing into strong 

 red ; black, changing into thin grey and yellow strata ; warm grey 

 again, passing into deep red; and, at the base, warm grey, alternat- 

 ing with thin strata of many colours, too numerous to recapitulate. 

 The lower series commences at the top with a stratum of reddish - 

 grey colour for about half the whole depth of the cliff ; then a 

 stratum of ashy grey, followed by a strong black band ; Indian red, 

 succeeded by more black strata ; and terminating at the base with 

 a bed about 200 feet thick, of strongly reddish hue. 



With the exception of the lowest rocks of the lower series, it is 

 impossible to collect examples of these strata in situ, as the cliffs 

 are well-nigh vertical ; but specimens from all of the beds in the 

 upper series (knocked off by the descent of the ice-avalanches) can 

 be obtained on the surface of the Glacier de Debris, and they are 

 found to be entirely volcanic products — principally andesitic lavas. "^ 

 The colouring is superficial, the result of weathering, or decom- 

 position. The natural colours of these rocks range from steel and 

 iron-greys to purplish -black. 



A great section of a somewhat similar nature was produced on 



1 It is not unlikely that this is the rock we obtained at 19,400 feet upon the 

 first ascent. See pp. 67-8. 



2 Amongst these fragments on the glacier I found native sulphur. 



