232 REV. W. THORP, B.A.— AGRICULTURAL GEOLOGY, ETC. 
about 600 yards thick, and contains the most productive and richest 
number of coal-seams ; the upper portion, of about 300 yards, con- 
sisting entirely of coarser arenaceous beds, the coals covering only 
small areas. The several seams of coal, their position, quantity and 
quality, were described in great detail, and illustrated by reference 
to various sections. The average vertical thickness of solid coal in 
Yorkshire is stated to be from 90 to 100 feet ; and Humboldt asserts 
that in the temperate zone the growth for 100 years of the forests 
upon any given part would not cover it seven lines in thickness with 
carbon ; therefore, in order to account for the enormous quantities 
and sizes of the plants which compose the coal strata, we must 
enquire into the forces which are concerned in the organizations of 
plants. A gTeat quantity of carbonic acid in the atmosphere, together 
with an increase of temperature, have been assigned as sufficient 
causes for this luxurious vegetation ; and from the researches of Dr. 
Draper, of New York, light, or rather the tithonic rays, are the active 
agents in the growth of all vegetation ; he asserted that the sun is 
one of the periodical stars, and that for a series of years or centuries 
it may increase in brilliancy, and then decrease, which would affect 
the rate of vegetable growth, and the character and constitution 
of the atmosphere. It has been objected that such alternations 
would require long periods of time, but " of one thing we may 
rest assured that no matter how great the periods that may 
be required for the phenomena of the universe to transpire, 
there has been and will be time enough for their endless repeti- 
tion." The paper was hstened to by Professor Phillips, Sir 
Roderick I. Murchison, and Dr. Buckland. At its conclusion 
Professor Phillips congratulated the Society on hearing the result of 
many years' hard work among the coal-fields in Yorkshire, and he 
hoped that Mr. Thorp would publish the result of his experiences at 
length in the transactions of the Society. Dr. Buckland, Dean of 
Westminster, offered some remarks in favour of the theory that coal 
was a vegetable construction. He affirmed it to be the unanimous 
opinion of competent persons that the coal-fields were derived from 
vegetable origin grown upon the spot, and after seeing Mr. Thorp's 
sections he was confirmed in that opinion. Sir Roderick Murchison 
