SOO Dr Daubeny on the Ancient Volcanoes of Auvergne. 
This attracted the attention of Professor Hansteen, and, after 
having further extended his observations on this point, he obtain- 
ed the general result, that at the | 
foot N of any vertical object SN', * 2 
the cylinder oscillates quicker in 
«, to the north end thereof, and 
slower in h to the southward 
thereof ; but on the contrary, 
at the upper part S, it oscillates 
quicker on the south side at d, | 
and slower on the north side at * 
c. Hence, he draws the conclusion, that every vertical object, 
of whatever material it is composed, has a magnetic south pole 
above, and a north pole below. 
Art. X. — On the Ancient Volcanoes of Atwergne. By Charles 
Daubenv, M. D. M. G. S. and Fellow of Magdelane Col- 
lege, Oxford. In a Letter to Professor Jai^iesox. 
Dear Sir, 
In my former communication, I took notice of the Volcanic 
Rocks found in the immediate neighbourhood of Clermont, all 
of which, with the exception of a few mountain caps.^ composed 
of basalt, which were mentioned in the close of my letter, ap- 
peai’ed to me of post-diluvian origin, I shall next proceed to 
another class of rocks, which, although probably belonging to 
the same general head, seems, nevertheless, to present several 
important differences. 
The Mont d’Or range of Hills, which is the principal sub- 
ject of the present paper^ must, I believe, be referred exclusive- 
ly to the class of Ancient Volcanoes, inasmuch as they are found, 
like the rocks on which they lie, at equal levels, on either side 
of the valleys v/hich intersect them ; and, therefore, if we sup- 
pose that they were once in a state of fluidity, a point which I 
hope afterwards to be able to establish, evidently prior to the 
formation of the latter. s 
