iv Hutton verifies his Theories 161 



that could call forth such strong marks of joy and 

 exultation." 



Another of Button's fundamental generalizations was 

 tested in as vivid and successful a manner. He taught 

 that the ruins of an earlier world lay beneath the secondary 

 strata, and that where the base of these strata can be seen, 

 it will be found to reveal, by what is now known as an 

 unconformability, its relation to the older rocks. He had 

 at various points in Scotland satisfied himself by actual 

 observation that this relation holds good. But he deter- 

 mined to verify it once more by examining the junction of 

 the two groups of rock along the coast where the range of 

 the Lammermuir Hills plunges into the sea. Accompanied 

 by his friend Sir James Hall, whose property of Dunglass 

 lay in the immediate neighbourhood, and by his colleague 

 and future biographer Playfair, and favoured by calm 

 weather, he boated along these picturesque shores until the 

 unconformable junction was reached. The vertical Silurian 

 shales and grits were found to protrude through and to be 

 wrapped round by the red sandstone and breccia. " Dr. 

 Hutton," Playfair writes, " was highly pleased with ap- 

 pearances that set in so clear a light the different formations 

 of the parts which compose the exterior crust of the earth, 

 and where all the circumstances were combined that could 

 render the observation satisfactory and precise. On us 

 who saw these phenomena for the first time, the impression 

 made will not easily be forgotten. The palpable evidence 

 presented to us of one of the most extraordinary and 

 important facts in the natural history of the earth, gave 

 a reality and substance to those theoretical speculations 

 which, however probable, had never till now been directly 



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