362 Prof. Bischof on the Natural History of 



nels to conduct the water from the surface as there are thermal 

 springs, or at least groups of thermal springs. Granting all 

 this, the question yet remains to be answered, why the effects 

 of these subterraneous oxidations are seen on the surface, in 

 and near volcanos only ; and why not even a trace of such pro- 

 cesses can be detected in other places, which yet present innu- 

 merable thermal springs ? Surely no one will bring forward 

 the scanty evolutions of sulphuretted hydrogen gas from sul- 

 phurous waters as proofs of such processes. But, were the 

 conditions necessary for volcanic activity fulfilled by the access 

 of water to the interior in each of these channels, then would 

 the occurrence of volcanic phenomena be much more frequent 

 on our earth. Or, it must at least be assumed that they were 

 at a former period as universally distributed as thermal springs 

 now are ; and that they have left behind a high temperature in 

 the interior, which warms the springs, and, as Daubeny also as- 

 sumes, extricates from the limestones, in the interior, the carbo- 

 nic acid gas so universally present. That this is occasionally 

 the case, namely that springs do acquire their heat at the ex- 

 pense of volcanic masses elevated at a distant period is certain- 

 ly true, and has probably been of still more frequent occur- 

 rence in former times. I have myself already adduced instances 

 of this kind. With the cooling of these masses, however, the 

 thermal springs dependent on them must of [course also cool, 

 and whether this cooling take place in a longer or shorter time, 

 jnust depend on the greater or less extent of those masses. 



After the preceding remarks, the question remains, whether 

 it be necessary to assume, in explanation of the universal dis- 

 tribution of thermal springs, a volcanic activity once so univer- 

 sally distributed ; or whether their existence cannot be both 

 more simply and more satisfactorily explained by an increased 

 temperature in the interior, which is by no means merely hy- 

 pothetical, but is supported by innumerable facts. 



Daubeny says,* " They (the supporters of my views) should 

 explain to us why primary rocks, traversed, as they so fre- 

 quently are, with fissures of all descriptions, should not in every 

 part of the world, and in every kind of situation, give rise to 



* Report, p. 70. 



