Professor Geikie on the " PitcJistone'' of Eshdale. 229 



duced into the problem by the assertion that during the 

 general subsidence there were occasional intervals when the 

 level of the sea rose again. By what conceivable mechanism 

 this rise took place is not explained. 



The existence and influence of subterranean heat were 

 quietly ignored by the Wernerians. They refused to recog- 

 nise any proofs of general subterranean heat, and consequent 

 volcanic action. They could not deny the existence of vol- 

 canoes, but they minimised their importance as much as 

 possible, regarding them as merely local and superficial 

 phenomena due to the inflammation of beds of subterranean 

 coal. They asserted that volcanoes occur only in coal dis- 

 tricts that have been covered with sheets of basalt, and that 

 the coal, undergoing spontaneous combustion with access of 

 water, gives out so much heat as to melt the overlying basalt, 

 and cause it to flow into the hollows, whence it is expelled by 

 the force of ascending aqueous vapour.* 



If modern volcanoes, with their copious outflows of lava 

 were thus explained, we need not wonder that the idea of 

 the existence of ancient lavas all over the world, of diverse 

 ages, and utterly independent of any coal deposits, was 

 ridiculed as one of the " monstrosities" of speculation against 

 which the sober, inductive spirit of Wernerianism had to 

 wage unrelenting warfare. So prejudiced were the Wernerian 

 geognosts that they refused to admit the igneous origin even 

 of obsidian and pumice, rocks in which an illiterate peasantry 

 had long recognised the traces of fire. They had even the 

 boldness to assert that pumice had been " ascertained to be 

 an aquatic product," because it alternates with basalt and 

 porphyry, passes into obsidian and pearlstone, and "has 

 never been observed to flow in streams from the crater and 

 sides of a volcano," and because " no one ever saw it forming 

 a stream in countries containing extinct volcanoes." -f- 



The genius of Werner may be estimated, if not from his 

 writings, certainly from the number of his followers and the 

 enthusiasm with which they left Freiberg to apply his 

 system to the elucidation of the geognosy of all parts of the 



* Jameson, op. cit. iii., p. 219. 

 t Jameson, op. cit, iii., p. 196. 



