Natural History of Volcanos and Earthquakes. 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 that 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 tobe perfectly arbitrary. Thermal springs (taken in this 
Sense, ) are very widely distributed over the globe, as I think I 
have formerly shown. Na , | 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. 
» like~Professor Daubeny,* we regard chemical processes 
oing on in the earth as the cause of thermal springs, then must 
these processes be as universally distributed as the thermal springs. 
Ose 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. 
