TRANSACTIONS OF THE SECTIONS. 
591 
ties Collines du Boccage : 1. in the chains of the Cumbrian 
lakes we find the transition formations ranging unconformably 
to the superincumbent carboniferous E.N.E. and W.S.W. ; 
2. in the Isle of Anglesea, N.E. and S.W. The same general 
direction prevails throughout Wales, and in Devonshire and 
Cornwall. Mr. Conybeare observes that the general parallelism 
of these transition chains is the circumstance in our island most 
in accordance with M. de Beaumont’s theory, with which how¬ 
ever the phenomena of the carboniferous chains have been 
seen to be very inconsistent. 
He concludes with the following remark. Finally, when 
the theory of parallel chains with reference to the points of 
the compass is so extended as to embrace half the circum¬ 
ference of the globe, (as is done in the conclusion of M. de 
Beaumont’s memoir*,) Mr. C. would inquire, Do we not require 
a more exact definition of the sense in which the term parallel 
is here used? The parallels of latitude are, indeed, strictly 
parallel lines; but the meridians are great circles passing 
through the centre of the planet, and no two of them can pos¬ 
sibly be parallel to one another. 
In the discussion which followed the reading of this memoir, 
Professor Sedgwick expressed his agreement with the general 
views of Mr. Conybeare, but added, that in the older strata of 
our Island the phsenomena appear to be in strict accordance 
with that part of M. de Beaumont’s theory which asserts that 
mountain chains of synchronous elevation are parallel. 
Mr. Sedgwick afterwards proceeded to give a verbal account 
of the geology of Caernarvonshire. He described the minera- 
logical structure of the country, and showed that the range of 
the beds is parallel to the direction of the mountain chain. 
The lowest of these strata are composed of mica and chlorite 
slate, containing masses of jasper, verd antique, and primary 
marble. The highest mountains are distinctly stratified, and 
not unfrequently contain organic remains, but are associated 
with masses of pseudo-breccia, compact felspar, and porphyry, 
generally arranged in masses exactly parallel to, and passing 
into, the true strata : the laminae of slaty cleavage, after pass¬ 
ing through the various beds of entire mountains, are seldom, 
if ever, parallel to the stratification. He then showed, by maps 
and sections, the existence of three or four parallel anticlinal 
lines, ranging nearly the whole length of the chain, and only 
deflected from their bearing when they interfere with other 
lines, produced by a local elevation ; and he stated, lastly, the 
* See Phil. Mag. and Annals, N.S. vol. x. p. 259, in an extract from M. de 
Beaumont’s Essay. 
