ii Desmaresfs Physiography 63 



where the volcanic origin had been more or less ob- 

 scured. 



It is at this point in his investigation that the genius 

 of Desmarest shines with a brilliance far above that of 

 any of his contemporaries who concerned themselves with 

 geological problems. Guettard had clearly indicated the 

 volcanic origin of the puys of Auvergne, and no great 

 acumen was needed to follow up the clue which he had 

 thus given. But to trace a pathway through the maze of 

 lavas of many different ages, to unite and connect them 

 all in one method of interpretation, and thus to remove 

 the endless difficulties and harmonise the many apparent 

 contradictions which beset the investigation, was a task 

 which called forth the highest powers of observation and 

 induction. Among the many claims of France to the 

 respect and gratitude of all students of geology, there 

 is assuredly none that ought to be more frankly 

 recognized than that, in her wide and fair domain, 

 she possessed a region where the phenomena were dis- 

 played in unrivalled perfection, and that in Desmarest 

 she could boast a son gifted with the skill, patience, 

 imagination, and originality that qualified him so admir- 

 ably for the laborious task which he undertook. His 

 achievements form one of the most notable landmarks in 

 the early history of geology. 



Desmarest, wandering over the volcanic districts of 

 Central France, had been profoundly impressed, as every 

 traveller must be, by the extraordinary varieties in the 

 condition of the various lava-currents. Some of these 

 sheets of rock retain still the dark, verdureless, rugged 

 surfaces which they assumed ages ago when their molten 



