198 Sir A. Geikie — Lamarck and Flay fair — 



Hutton ; the second part is composed of a series of valuable notes^ 

 further explaining and developing various parts of that system, and 

 containing original observations and deductions of Playfair's own, 

 together with discussions of those published by other writers. This 

 volume brought Button's " Theory of the Earth " within the com- 

 prehension and appreciation of even the most unscientific reader. 

 It not only revealed to mankind what a genius had passed away in 

 Hutton, but it traced out with admirable clearness some of the chief 

 routes along which geology has since travelled, and it imparted to 

 the infant science much of the impulse which has carried it to the 

 position which it now holds in the circle of human studies. 



In Playfair's glowing pages the excellences and the defects of his 

 master's system are faithfully reflected. Never before had so 

 eloquent and convincing a sketch been given of the co-operation of 

 underground and superficial agencies in the decay and renovation of 

 land, and in the perpetuation of the conditions that make this planet 

 a habitable globe. No previous writer had set in so clear a light 

 the sculpture of the land by the flow of rain and rivers across its 

 surface. Nor had the proofs of the presence of abundant intrusive 

 igneous rocks in the crust of the earth ever been so convincingly 

 marshalled, and this too at a time when the doctrine of Freiberg 

 everywhere prevailed that all these rocks have been deposited either 

 as precipitates or as sediments on the floor of the sea. 



His close personal association with Hutton had given Playfair 

 a keen appreciation of the vivid interest of geological questions and 

 of the nature of the evidence required for their solution. His own 

 philosophical temperament enabled him to form a calm judgment of 

 the relative value of the various lines of proof, and to trace with 

 precision the limits within which deductions might be logicallj' 

 drawn from them. Moreover, his excursions into the field under the 

 guidance of his master had given him a quickness and accuracy of 

 observation which in the end made him an excellent field geologist, 

 so that in his exposition of Huttoniau principles he is able from time 

 to time to appeal in their support to evidence which he has himself 

 collected. Bis " Notes " are thus full of personal interest in their 

 revelation of his extensive acquaintance with actual concrete 

 examples of the phenomena described. 



It was Playfair who first pointed out that " for the moving of 

 large masses of rock, the most powerful engines without doubt 

 which Nature employs are the glaciers," and who first maintained, 

 in opposition to De Saussure's invocation of some great debacle, that 

 the erratic blocks, scattered in such numbers over Switzerland, have 

 been dispersed by glaciers and rivers ( §§ 34:8-353). His reasoning 

 against the appeal to some gi"eat cataclysm in explanation of such 

 phenomena enabled him to sustain with much force Button's protest 

 against the tendency to have recourse to " accidental and unknown 

 causes." In a convincing argument he reviewed the hypothesis of 

 Bufi"on and Pallas as to the distribution of abundant remains of large 

 mammals over the plains of Siberia, and he showed that these 

 remains cannot have been brought either by an inundation of the 



