NATURAL HISTORY. 
Fermation, is a far more difficult matter. De Luc, 
who spent much time in the neighbourhood, always 
contended that a volcanic action was obvious in the 
sienitic rocks of the neighbeurhood of Bottor—as 
far as our own observation extends, between these, 
and the characters presented by many others along 
the eastern line of junction with the granite, there 
appears to be no sutiicient difference to justify the 
idea of their originating from distinct causes, or at 
different periods ; rocks of a compact basaltic cha- 
racter in which Hornblende predominates, and 
which frequently contain a large proportion of Lron 
(often from 15 to 20 per cent and upwards,) may 
be met with at various places along the whole line 
both in Devon and Corawall—it would require 
more extensive and accurate examination than has 
hitherto been afforded them, to pronounce with any 
degree of confidence, but we feel inclined to con- 
sider them as a series of Whin Dykes connected 
with the o/der members of the different rock series, 
as the Amygdaloidal Trap may probably be with 
the more recent ones.* 
* We have alluded to the great variety of structure pre- 
sented by the different rocks that we have placed together 
under this head, and an extract, from Humboldt’s Essay 
previously referred to, on this point may not be misplaced 
in a note. After propounding as the universal law of 
minerals, that all rocks were in the first instance, an amor- 
phous paste, the crystalline elements or molecules of which 
tho’ invisible to the eye, are found by degrees increased 
and disengaged from the close texture of the mass —he 
