Natural Histojy of Volcanos and Earthqualies. 53 



Their wide distribution, the invariableness of their phenom- 

 ena, the evolutions of gases from many of these, present to every 

 attentive observer, matter of investigation and consideration on 

 their origin, duration, and connection with other phenomena. If, 

 then, we can succeed in proving tliat chemical processes can 

 with much less probability be assigned as the cause of their be- 

 ing heated, that on the other hand, the most convincing reason 

 show that their heat is acquired at the expense of the interior of 

 the earth : then will the hypothesis, which endeavors to explain 

 volcanic phenomena from the same causes, gain no little increased 

 weight. And in fact if hot springs be heated to such a degree 

 as to attain the boiling point at a certain depth in the earth, we 

 have but one step to make, by supposing this heat increased up to 

 the fusing-point of volcanic stony masses, in order to attribute 

 with equal probability, volcanic phenomena and hot springs to the 

 central part of our earth. 



I must observe, in the first place, as was formerly remarked, 

 that, by thermal springs, I understand nothing more than springs 

 whose average temperature exceeds that of the soil at the level at 

 which they rise. It is therefore indifferent whether this excess 

 consists in 1° or less, or in 50° or more. I can form no other 

 idea of the meaning of the word thermal springs ; at least, I do 

 not know what degree of temperature can be laid down as the 

 boundary between cold and thermal springs, unless the distinction 

 were to be perfectly arbitrary. Thermal springs (taken in this, 

 sense,) are very widely distributed over the globe, as I think I 

 have formerly shown. Nay, I am convinced that, if we take 

 any district of nearly equal height above the level of the sea, 

 several of the springs will be found to exceed in average temper- 

 ature that of the soil. An exception to this rule will certainly 

 be found only in those situations where springs arise at the foot 

 of hills more or less high and which have acquired, a cooler tem- 

 perature from the higher regions. 



If, like Professor Daubeny,* we regard chemical processes 

 going on in the earth as the cause of thermal springs, then must 

 these processes be as universally distributed as the thermal springs. 

 Those who entertain these views, however, do not surely con- 



* Report on the present state of our knowledege with respect to mineral and 

 thermal waters. London, 1837. 



