in New Countries . 3 
the last few years, that it may be pardoned to any one 
who has not made the science his professed study, if he 
err in the application of the one, or miss the true bearing 
of the other. So much, indeed, do long-used terms and 
easily gained ideas cling to our mouths and understand¬ 
ings, that even with professed geologists some igneous 
rocks, such as granite, syenite, or porphyry, are looked 
upon and spoken of as necessarily primary or very 
ancient, and mineral characters alone arc used as sufficient 
to identify some aqueous formations. Not to.adduce too 
many examples of error on these points, it may be suffi¬ 
cient to single out that of Devon and Cornwall. The 
granites and slates of these counties were, by common 
consent, looked upon as the most ancient rocks of 
England,— as, par excellence , the primary portion of our 
island. Some difficulty, however, was felt by many re¬ 
specting the characters of the fossils which were procured 
near Plymouth and other places. In the year 1836, 
Professor Sedgwick and Mr. Murchison, at the meeting 
of the British Association at Bristol, declared their belief 
that the slates and limestones of Devon and Cornwall 
belonged to the Silurian formation. Further examina¬ 
tion, however, induced them to modify their ideas; and, 
with the aid of a suggestion from Mr. Lonsdale, they 
have thrown an entirely new light on the subject. The 
slates and other rocks, provincially called Killas, belong 
to two consecutive but slightly unconformable forma¬ 
tions : the upper portion contains impressions of plants, 
some black limestones with Posidonice , and a few beds oi 
culm or anthracite, and is the representative of the car¬ 
boniferous system; the lower portion is full of marine 
shells and corals, of a character intermediate between the 
fossils of the carboniferous and Silurian systems. It there¬ 
fore occupies the place of the old red sandstone, and is 
now erected into a separate system which is called Devo- 
b 2 
