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[[underline]] 1892 [[/underline]] [[underline]] December 5. - Continued [[/underline]] rest of the exposures show only Columbia brick clay, and this is also the case with all between here and the White House Bluff proper, which begins just west of the extreme easterly point of land on this neck. Here the Potomac suddenly rises up with first only the Columbia, but soon with a heavy bed of Marine Tertiary, mostly Chesapeake overlying it. The boundary between this latter and the Potomac has furnished one of the most difficult problems I have encountered. The entire extent of the Potomac along the shore above this point is less than half a mile, and it terminates as abruptly as it begins immediately above the original plant bed of Prof. Fontaine Midway of its extent there is a log-slide, and the bluff has here reached a height of some 70 or 75 feet. The white kaolinic sand rock at the base is here hardened into free-stone, less firm than but generally similar to that of Aquia Cr. and Point of Rocks. The following is a section at and below the log-slide: [[end page]] [[start page]] [[three columns, indicated in transcription by |]] 6 | Columbia brick clay | 6 feet 5 | " [[Ditto for: Columbia]] gravel and cobble | 5 " [[Ditto for: feet]] 4 | Clay, light colored weathering red or mottled, and cracking into small square blocks, greenish and less broken below, clearly Chesapeake | 4 " [[Ditto for: feet]] 3 | Coarse or firmish stratified and cross-bedded sands, yellow, brown, gray, blueish, or jet black, with thin sheets of ferruginous rock or shale, sometimes tending towards concretions and rarely horizontal, with many green clayey pellets, pockets, lenses, or strata, the latter sometimes reduced to lines of fine lumps | 3 " [[Ditto for: feet]] 2 | Coarse sand with less inclusions, but otherwise not distinguishable from No. 3 | 10 " [[Ditto for: feet]] 1 | Coarse kaolinic white lithified sand or freestone rock with clay balls, lenses &c., some of them green and glauconitic, also rounded quartz pebbles | 20 " [[Ditto for: feet]] [[line indicating addition]] Total 75 " [[Ditto for: feet]]
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