CHAP. xxiv. CHANGES OF SEA AND LAND. 419 



confusion. Wide areas of seas were depopulated, but 

 the dead fish remained. They were left in the mud. 

 The mud and fish became Caithness flag now the 

 support of a large population. " Thus Thurso itself," said 

 Dick, " is built of dead fish." 



But that time passed away, and the sea went rolling 

 over Caithness. Ponderous glaciers went grating along 

 the mountain sides of the Scaraben range, grinding its 

 rocks down into clay, and strewing the deep-sea bottom 

 with gigantic boulders. Amongst the boulders and 

 boulder clay, which forms a large part of the county of 

 Caithness, Dick found the numerous marine shells which 

 have been described in the previous pages. 



All this was very mysterious to Dick. The preoccu- 

 pancy of the seas by the fishy tribes, and the present joint 

 tenancy of the land by man and the lower creation, 

 were two striking facts which strongly impressed his 

 imagination. Might not this be the first cycle of the 

 geological manifestation of the globe; or rather the 

 first of a series of cycles, at whose close the existing 

 races of living beings, and the gorgeous fabrics of 

 national vanity, shall yield their haughty relics to the 

 sport and desolation of the elements, when new heavens 

 and a new earth shall replace the ruins of a world ? 



Although Dick devoted a great part of his spare time 

 to botany, it was to geology that he devoted so large a 

 share of his attention. It was MantelTs Wonders oj 

 Geology that first attracted him to the subject; then 

 Buckland's Bridgewater Treatise, and after that Hugh 

 Miller's Old Red Sandstone. He had already found 



