1 60 The Founders of Geology LECT. 



affirmed to be the earliest chemical precipitate from his 

 primeval ocean, was surmised by Hutton to be of igneous 

 origin, and he believed that, if its junctions with the 

 surrounding strata were examined, they would be found to 

 furnish proofs of the correctness of his inference. The 

 question could be easily tested in Scotland, where, both in 

 the Highlands and among the Southern Uplands, large 

 bodies of granite had long been known to form important 

 groups of mountains. Accordingly, during a series of 

 years, Hutton undertook a number of excursions into 

 various parts of his native country, and returned from each 

 of them laden with fresh illustrations of the truth of the 

 conclusions at which he had arrived. At one time he was 

 busy among the roots of the Grampian Hills, at another 

 he was to be seen scouring the lonely moorlands of Gallo- 

 way, or climbing the precipices and glens of Arran. His 

 visit to Glen Tilt has been made memorable by Playfair's 

 brief account of it. 1 He had conjectured that in the bed 

 of the river Tilt actual demonstration might be found that 

 the Highland granite has disrupted the surrounding 

 schists. Playfair describes how " no less than six large 

 veins of red granite were seen in the course of a mile, 

 traversing the black micaceous schistus, and producing, by 

 the contrast of colour, an effect that might be striking even 

 to an unskilful observer. The sight of objects which 

 verified at once so many important conclusions in his 

 system, filled him with delight ; and as his feelings, on 

 such occasions, were always strongly expressed, the guides 

 who accompanied him were convinced that it must be 

 nothing less than the discovery of a vein of silver or gold 



1 Button's account is in the unpublished third volume of his Theory, 



