372 RAMBLES OF A GEOLOGIST. 



scratched glass ; and pure white quartz into porcellanic trails 

 of white, that ran in one instance along the face of a darker- 

 coloured rock below, like streaks of cream along the sides of 

 a burnt china jug. In one mass of pale large-grained granite 

 I found that the feldspar, though it had acquired a vitreous 

 gloss on the surface, still retained its peculiar rhomboidal 

 cleavage ; while the less stubborn quartz around it had be- 

 come scarce less vesicular and light than a piece of pumice. 

 On some of the other masses there was impressed, as if by a 

 seal, the stamp of pieces of charcoal ; and so sharply was the 

 impression retained, that I could detect on the vitreous sur- 

 face the mark of the yearly growths, and even of the medul- 

 lary rays, of the wood. In breaking open some of the others, 

 I detected fragments of the charcoal itself, which, hermeti- 

 cally locked up in the rock, had retained all its original car- 

 bon. These last reminded me of specimens not unfrequent 

 among the trap-rocks of the Carboniferous and Oolitic sys- 

 tems. From an intrusive overlying wacke in the neighbour- 

 hood of Linlithgow I have derived for my collection pieces 

 of carbonized wood in so complete a state of keeping, that 

 under the microscope they exhibit unbroken all the charac- 

 teristic reticulations of the coniferse of the Coal Measures. 



I descended the hill, and, after joining my friends at Strath- 

 pefier, Buchubai Hormazdji among the rest, visited the 

 Spa, in the company of my old friend the minister of Alness. 

 The thorough identity of the powerful effluvium that fills the 

 pump-room with that of a muddy sea- bottom laid bare in 

 warm weather by the tide, is to the dweller on the sea-coast 

 very striking. It is identity, not mere resemblance. In 

 most cases the organic substances undergo great changes in 

 the bowels of the earth. The animal matter of the Caith- 

 ness ichthyolites exists, for instance, as a hard, black, insoluble 

 bitumen, which I have used oftener than once as sealing-wax : 

 the vegetable mould of the Coal Measures has been converted 



