262 PROGRESS OF SCIENCE IN THE CENTURY. 



present ends to the far-distant crests of the 

 Jura." * In fact the proof might be taken as a 

 model of scientific inference. 



The Drift Theory. In spite of the conclusive 

 researches of Agassiz and Charpentier, equally able 

 men refused to be convinced. Thus Leopold von 

 Buch and many adherents delayed the recognition 

 of the ancient glaciers by a theory of great floods, 

 supposed to have borne Northern blocks even to the 

 foot of the Alps. On the other hand, the polar 

 experiences of Parry, Scoresbv, and Ross led some 

 British geologists Lyell, De fa Beche, Charles Dar- 

 win, and Roderick Murchison to a "drift-theory," 

 which supposed the transport of erratic material by 

 icebergs, and in this they were supported by Both- 

 lingk, Bronn, Forchhammer, Frapolli, and others.f 

 The influence of this " drift-theory " which seems 

 a big error enclosing a fragment of truth was con- 

 siderable, and lasted till 1879 when Penck had the 

 satisfaction of giving a merciful death-blow to a 

 theory which was slowly dying of inanition. 



It would require a great expert to select wisely 

 from the succession of events, but perhaps we may 

 associate the next great step with Andrew Crombie 

 Ramsay who made a profound study of the glacia- 

 tion of Scotland and Wales (1854), detected traces 

 of at least two ice ages, and inferred the existence 

 of glaciers in the Permian. This revived the idea 

 of recurrent ice ages. Very important, also, were 

 the observations on the existing glaciers of Green- 

 land from those of Rink (1857) to those of Torell 

 (1872), and onwards to those of Nansen. 



That evidences of glaciation were obvious in 

 countries now free from glaciers, that there had been 

 * Founders of Geology, p. 273. f Zittel, op. cit., p. 342. 





