GEOLOGY OF BUTE. 



321 



to whose examination the best specimens that could be 

 selected were submitted, in order that he might determine 



Fig. 39. 



s, Sandstone; r, terrace and road;//, greenstone; a, trap-tuff; 6, red 

 ochre ; c, lignite bed ; d, pisolitic ochre ; e, porphyritic amygdaloid, the 

 upper portion much altered. 



the species of wood, but without any note of the geological 

 situation of the coal, was "unable to obtain a slice, in conse- 

 quence of the structure being altered by the contact of a 

 whin dike." The coal has been worked to some extent 

 by driving an adit inwards on the line of the dip, which is 

 about 20 to the westward ; but the workings have been for 

 some time abandoned, and the inner and lower portions are 

 now full of water. 



The floor of the coal has been already described. The 

 roof is a peculiar rock. It consists of a base or paste of an 

 ochreous steatite, with imbedded round pieces of the same 

 substance, and may hence be called a pisolitic ochre; it is 

 three and a-half yards thick. The bed above this is of the 

 same character; but the base feels less unctuous, and with 

 the imbedded steatite it contains also imbedded calcareous 

 spar. The base effervesces briskly with an acid ; and hence 

 we may call the rock a calcareous amygdaloid. The upper 

 portion of this bed, to the thickness of a few inches only, is 



