$14 Dr Daiibeny on the Arwlent Volcanoes of ’ dtivergnc. 
theless, feel themselves compelled to admit the trap-rocks above 
mentioned as volcanic, from their analogy with those of the 
Giant’s Causeway ! Even such as, with Dr MacCulloch, in- 
clude granite among the products of Fire, or, even with my in- 
genious friend Dr Boue, broadly assert that all rocks, at least as 
far down as sandstone, which are not of mechanical origin, must 
be referred to this agent, cannot but be puzzled at the resem- 
blance subsisting between certain varieties of granite and of the 
old red sandstone. 
Since, therefore, it seems to follow, that Fire and Water, al- 
though such opposite agents, have, in some instances, produced 
effects nearly, if not altogether identical, I do not see that the 
geologist who returns from Auvergne, persuaded that great 
part at least of what has been called the Newest Floetz-Trap 
Formation of Werner is of volcanic origin, ought to be accused 
of inconsistency, if he still hesitates as to the real origin of those 
rocks, which, if, in their external characters, they approach to the 
latter, would seem, nevertheless, from their repeated alternations 
with sandstone, and other strata of a similar description, to be 
of Neptunian origin themselves • **. 
I had intended adding some remarks on the Fresh Water 
Formation of Auvergne ; but as the present memoir has already 
• Those of your readers who may recollect what I said in my former letter re- 
specting the Puy Marmont, where trap- rocks which were assumed to be of igneous 
origin are described as alternating with a fresh-water limestone, may object to the 
present conclusion as inconsistent with the former statement. I have nowhere, 
however, denied the possibility of an alternation of volcanic rocks with the pj’o- 
ducts of aqueous deposition, the actual occurrence of which is indeed sufficiently 
established, by the observations of those who have travelled in countries admitted 
to be volcanic ; but, on the other hand, it will, I think, be allowed that the 
probability of such an accident diminishes in the direct ratio of the number of such 
•alternations, and, therefore, that those who do not go so far as to consider the sie- 
siite and greenstone rocks of Primitive Districts as volcanic, and consequently see 
nothing in the structure and composition of hornblende or augite rocks in general, 
which stamps them as the Products of Fire, will regard such a succession of beds 
as that which meets our eye on the Fife coast, from Kinghorn to Kirkcaldy, as 
more probably referable to one agent, and that water, than to the alternate influ- 
ence of two opposite forces, repeatedly giving wa,y, qs if by consent, one to the 
other. 
