94 Mr Anderson on the Bituminous Hock of Uoss-shirc. 



into which the quartz rock, that formed the subject of my 

 paper, passes, are the common old red sandstone, and a 

 grey and very micaceous sandstone, soft and extremely fissile. 

 The simple minerals found in the sandstone are pyrites, green 

 earth, or earthy chlorite, heavy spar, occasionally arragonite, 

 and foliated celestine, together with large well-defined crystals 

 of prismatic calcareous spar. 



But, as I have hinted, {see page 217 of the last Number) 

 the most interesting association of the sandstone is with strata 

 of a bituminotis rock, hitherto but little noticed by geologists. 

 By some it has been regarded and passed over as a subordi- 

 nate variety of graywacke slate ; and it has been occasionally 

 called a transition clay-slate, or a secondary shale. 



But its analysis, I understand, has not yet been given to 

 the public ; and its relations to rocks, so high in the series as the 

 older sandstone, have not been thoroughly investigated. In 

 the district now under consideration, the exact geological po- 

 sition of this rock may be described as being immediately 

 above the old red sandstone. It appears on the acclivities of 

 the conglomorate range of hills, between the quartz rock and 

 stratified sandstone, and hence another very important dis- 

 tinction is afforded between these two rocks. 



If again we trace this bituminous rock along the course of 

 the River Beauly, we shall find that it possesses similar rela- 

 tions. In the valley of Strathpeffer, in Ross-shire, it is pro- 

 bable that the mineral waters, so highly impregnated with sul- 

 phuretted hydrogen in that neighbourhood, derive some of 

 their properties from their passage through this interesting 

 bituminous compound. I have lately also seen specimens of 

 a similar bituminous rock, which was found associated with 

 the sandstone formations of Orkney. The external charac- 

 ters of the rock may be now described. 



It resembles the slate-clay, or bituminous shale of seconda- 

 ry districts, in the loose and thin slaty mode of its arrange- 

 ment, and in its tending to decompose into an iron-shot, or 

 ochry clay. When fresh, however, it is heavier than slate- 

 clay, and the structure, which in the large is slaty, is in the 

 cross fracture uneven and conchoidal, with a glimmering 

 lustre, derived from numerous minute scales of mica. Its 

 streak is white or grey, and when smartly struck, (especially 



