CHAP. XXV.] GEOLOGY. 89 



gullies may now be seen intersecting most incon 

 veniently the main street of Tuscaloosa, and several 

 torrents are cutting their way backwards through 

 the &quot;cretaceous&quot; clay, sand, and gravel of the hill on 

 which the Capitol stands. They even threaten in a 

 few years to undermine that edifice. I had observed 

 other recent ravines, from seventy to eighty feet deep, 

 in the Eocene strata between Macon and Clarkes- 

 ville (Alabama), where the forest had been felled a 

 few years before. 



On my way back from Tuscaloosa to Mobile, I had 

 a good opportunity of examining the geological struc 

 ture of the country, seeing various sections, first of 

 the cretaceous, and then lower down of the tertiary 

 strata. The great beds of gravel and sand above 

 alluded to, forming the inferior part of the cretaceous 

 series, might from their want of consolidation be 

 mistaken for much newer deposits, if their position 

 on the Tombeckbee, as well as on the Alabama river 

 at Montgomery, were not perfectly clear. They 

 pass beneath the great marlite formation, full of cre 

 taceous shells, which gives rise to the prairie soils 

 before described*, as nearly destitute of natural wood, 

 and crossing Alabama in an east and west direction. 

 These I examined at Erie, at Demopolis, and at 

 Arcola, where they contain hippurites and other 

 characteristic fossils. The depth to which they have 

 sunk Artesian wells through them in many places 

 (between 500 and 1000 feet), is astonishing. One 

 boring through blue marl and limestone at Erie, in 



* Ante, p. 42. 



