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TRANSACTIONS OP THE 



mile distant, is a bed of horizontal rock 50 feet in thick- 

 ness. The upper portion of this bed is entirely composed 

 of sand scarce agglutinized, which, on descending, passes 

 into a conglomerate of the same sand with quartz peb- 

 bles varying in size from that of a millet seed to a ton in 

 weight. This rock has a grey appearance, and the 

 harder varieties are quarried and used for building pur- 

 poses. In the county of Stafford, opposite to Frede- 

 ricksburg, this formation again occurs, formhig those 

 hills which border the river. These beds must have a 

 thickness of nearly 80 feet above the river. The lower 

 portion is a conglomerate similar to that which occurs 

 east, and of which we have just spoken, and disappears 

 under the tide waters of the Rappahannock. The upper 

 portions of these beds at this locality have a much finer 

 texture ; rolled pebbles are common, but differing from 

 the quartz pebbles of the lower stratum. These upper 

 beds are of a blue colour, argillaceous, and free from car- 

 bonate of lime. The imbedded pebbles appear to be 

 portions of a similar reck rolled. They, like the mass 

 of rock, contain many impressions of plants. Lignites 

 are common, and large portions of this rock abound 

 with impressions : specimens of fossil wood are found; and 

 in the same piece you have the quartzose petrifaction, 

 and the organic fibre not yet entirely replaced by the 

 silex. Sulphuret of iron, though not abundant at this 

 particular locality, is common in the environs. Portions 

 of the upper beds of these rocks are coloured yellow with 

 sulphur, which sometimes incrusts and forms concretions 

 in the cavities. The sulphur is most probably the result 

 of the decomposition of pyrites. 



The mass of grey rock is overlaid by three or four 

 feet in thickness of thin strata varying in composition 

 and differing from the main mass ; one of these strata is a 

 blue argillaceous bed six inches to a foot in thickness, 

 which divides easily, and displays to view fine impres- 



