CHAP. XXL] SILICIFIED SHELLS AND CORALS. 17 



lignite, the concentric rings of annual growth being 

 visible. Receding from the granitic rocks, six or 

 eight miles still farther to the south-east, I found 

 at Brown Mountain, a bluff on the Ocmulgee river, 

 and at other places in the neighbourhood, a great 

 many siliceous casts of fossil shells and corals, and 

 among others a large nautilus, the whole indicating 

 that these beds of cherty sandstone and impure lime 

 stone belong to the Eocene period. 



As there is much kaolin in this series of chert and 

 burr-stone strata, I have little doubt that the petri 

 faction of fossil wood, and of shells and corals, has 

 taken place in consequence of the decomposition of 

 the imbedded felspathic rocks and crystals of felspar, 

 taking place simultaneously with the putrefaction of 

 the organic bodies. The silex, just set free from its 

 chemical combination in the felspar, would replace 

 each organic particle as fast as it decayed or was re 

 solved into its elements. 



From Macon I went to Milledgeville, twenty-five 

 miles to the north-east, the capital of Georgia. 

 Instead of taking the direct road, we made a detour, 

 going the first thirty miles on the Savannah railway, 

 to a station called Gordon, where we found a stage 

 coach ready to drag us through the deep sands of the 

 pine-barrens, or to jolt us over corduroy roads in the 

 swamps. As we were traversing one of the latter, at 

 the rate of half a mile an hour, I began to contrast 

 the speed of the new railway with stage-travelling. 

 Our driver maintained that he could go as fast as the 

 cars. &quot; How do you make that out ? &quot; said I. &quot; Put 

 a locomotive,&quot; he replied, &quot; on this swamp, and see 



