RAMBLES OF A GEOLOGIST. 335 



wards, is the altered colour of the boulder-clay, as exhibited 

 iii ditches by the way-side, or along the shore. It no longer 

 presents that characteristic red tint, borrowed from the red 

 sandstone beneath, so prevalent over the Black Isle, and in 

 Easter Ross generally ; but is of a cold leaden hue, not unlike 

 that which it wears above the Coal Measures of the south, or 

 over the flagstones of Caithness. The altered colour here is 

 evidently a consequence of the large development, in Ferin- 

 donald and Strathpeffer, of the ichthyolitic members of the 

 Old Red, existing chiefly as foetid bituminous breccias and 

 dark-coloured sandstones : the boulder-clay of the locality 

 forms the dressings, not of red, but of blackish-gray rocks ; 

 and, as almost everywhere else in Scotland, its trail lies to 

 the east of the strata, from which it was detached in the cha- 

 racter of an impalpable mud by the age-protracted grindings 

 of the denuding agent It abounds in masses of bituminous 

 breccia, some of which, of great size, seem to have been drifted 

 direct from the valley of Strathpefier, and are identical in 

 structure and composition with the rock in which the mineral 

 springs of the Strath have their rise, and to which they owe 

 their peculiar qualities. 



After walking on for about eight miles, through noble woods 

 and a lovely country, I struck from off the high road at the 

 pretty little village of Evanton, and pursued the course of the 

 river Auldgrande, first through intermingled fields and patches 

 of copsewood, and then through a thick fir wood, to where the 

 bed of the stream contracts from a boulder-strewed bottom 

 of ample breadth, to a gloomy fissure, so deep and dark, that 

 in many places the water cannot be seen, and so narrow, that 

 the trees which shoot out from the opposite sides interlace 

 their branches atop. Large banks of the gray boulder-clay, 

 laid open by the river, and charged with fragments of dingy 

 sandstone and dark-coloured breccia, testify, along the lower 

 reaches of the stream, to the near neighbourhood of the ich- 



