252 Prof. Daubeny on Sir H. Davy’s Theory of Volcanos, 
simpler hypothesis” will account for the chemical phenomena 
accompanying volcanic action, and Dr. Davy himself not 
having supplied this desideratum, I cannot view his adoption 
of it in any other light at present than as a matter of taste on 
his part. Dr. Davy, indeed, makes his brother say, though I 
have not yet lighted upon the passage in which this sentiment 
occurs, that the chemical theory does not rest on sufficient 
evidence. 
This however, although a ground for scepticism as to the 
truth of the one, would afford no reason for adopting the 
other ; for granting that of two hypotheses both competent to 
explain the facts, the simpler one ought to be preferred, no 
competition surely can exist between them, when this can 
be predicated only of one. 
That the chemical theory will enable us to account for the 
phenomena, has beenshown in the memoir which called forth 
Dr. Davy’s animadversions, and since more fully elsewhere*, 
and is admitted, as has been seen, in the fullest manner by 
Sir Humphry in the very paper to which allusion is made. 
Neither do I see the force of the negative evidence which Dr. 
Davy has produced to impugn it, for he is too conversant 
with volcanic operations to be ignorant that sulphuretted hy- 
drogen is amongst its commonest products, and is too good a 
chemist to admit the possibility of substances like potassium 
or calcium in their unoxidized condition finding their way up- 
wards in the midst of the steam, which always accompanies 
volcanic ejections}. What, then, becomes of the objection, that 
if the hypothesis were correct, inflammable gas might proba- 
bly be detected issuing from the volcano, or that some pure 
or uncombined alkaline or earthy inflammable basis might be 
discovered entangled in the lava, when the former is seen to 
be actually present, and the latter can so little be expected ? 
And, whilst the presence of hydrogen, combined as it naturally 
would be with the sulphur which we know to exist in such 
situations, furnishes a striking confirmation of Sir Humphry 
Davy’s original views, neither he, nor any other chemist, has 
succeeded in accounting for it according to the opposite ones. 
The same may be said of the sal ammoniac, the nitrogen, 
and according to the simplest form of the hypothesis as ex~ 
* Encyclop. Metrop., art. GEoLocy. 
+ This objection, at least, cannot have originated with Sir Humphry, 
but must be the exclusive property of his brother, for in the memoir re- 
ferred to we find Sir Humphry distinctly asserting, ‘‘ That the extreme 
facility of oxidation belonging to these bodies, must prevent them from ever 
being found in a pure combustible state in the products of volcanic erup- 
tions. 
