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 

 drifted 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 in the 

 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 

 continued nearly uninjured till the evening of Sept. 16, 1833, 

 when there occurred a single loud report, with an upward move- 



Vo!. xLi, No. 1.— April-June, 1841. 8 



