Proceedings of the British Association. _ 57 
Turner, in their application of chemistry to geology ; and he had 
been requested by the Association to draw up a report of this ap- 
plication. He now brought forward his investigations on the 
~ most important of our mineral productions,—coal. Although 
some geologists may entertain a different opinion, he assumes for 
granted, the vegetable origin of coal; and although it may be 
classified in various ways for economic or geological convenience, 
as into caking or not caking, bituminous or not bituminous, the 
true basis of the classification must depend on the chemical com- 
position. Carbon, oxygen, and hydrogen, are the components of 
living vegetables, and the same elements compose coal, but in diffe- 
rent proportions. In the decomposition of vegetable matter there 
are two agents always at hand, viz. air and water, which resolve 
it into carbon, oxygen, and hydrogen, forming with one another 
these combinations; carburetted hydrogen, carbonic acid, and 
water. In the change from lignin to fossil wood, we find that 
carbonic acid is parted with ; and this continues without varia- 
tion in all the kinds down to cannel coal. In mines of lignite 
and cannel coal we find only carbonic acid, (or choke-damp ; ) 
while in mines of coal lower in the scale, we find in addition, 
carburetted hydrogen, (or fire damp ;) the hydrogen diminishing 
in each variety as we approach the anthracite. In regard to the 
question whether the vegetable matter that formed coal had been 
fed or generated on the spot, he was inclined to the latter 
~ Opinion. 
Mr. Mathie Hamilton presented “ Observations on great earth- 
quakes on the West coast of South America, particularly the great 
one of Sept. 18, 1833, which destroyed the city of Tacna, and 
other places in Peru.” 'Tacna, an Indian town of some antiqui- 
ty, now capital of the province of the same name, lies inthe 
midst of a desert tract of about 50 miles broad, between the 
mountains and the sea. The port of Arica, about 40 miles dis- 
tant, had, since the first arrival of the Spaniards, been five times 
destroyed by earthquakes, while Tacna had enjoyed a happy im- 
munity, and was supposed beyond the reach of this calamitous 
Visitation. After 1826, however, very frequent and severe shocks 
were felt, particularly a few weeks previous to the great one of 
Oct. 8, 1831, which reduced Arica to a heap of rubbish ; yet it 
ccatinnts’ nearly uninjured till the evening of Sept. 16, 1833, 
when there occurred a single loud mes with an upward move- 
Vol. x11, No. 1.—April-June, 1841. 
