PEAT. 359 



these d^^posits in several places. This sandstone (Map, plate I), occurs in 

 places along the eastern exposure of the crystalline rocks and extends for 

 some distance below the head of tide. The rock is usually variable in 

 texture, light gray or buif in color, and is composed chiefly of quartz and 

 feldspar, the feldspar often decaying rapidly on exposure. The individual 

 grains vary much in size, ranging from bird shot in size up to several 

 inches in diameter. 



In the early part of the last century much stone was quarried from 

 the Patuxent formation near the mouth of Aquia Creek for use in the 

 construction of public buildings in Washington. The Aquia Creek quar- 

 ries were purchased by the United States Government in 1791 for the 

 purpose of using the stone in the construction of public buildings in 

 Washington. The stone from these quarries was used chiefly in the con- 

 struction of many of the older public buildings in the above city, but the 

 quarries were abandoned many years ago largely, it is said, because of 

 the unfitness of the stone for exposed work. The old light house at Cape 

 Henry was also constructed from the same kind of stone. On the Kappa- 

 hannock Eiver near Fredericksburg, and on the Appomattox Eiver near 

 Bermuda Hundred, similar material has been quarried for local uses. 

 Some of this sandstone is very firmly indurated and forms a fairly good 

 building stone that proves very durable, but in quarrying it much of the 

 rock has to be wasted because of the pockets of loose sand which are 

 frequently encountered. 



The indurated marls of Eocene and Miocene age are widely distributed 

 throughout the Coastal Plain and have furnished much material for the 

 construction of foundations. These stones are not especially durable 

 and they cannot be dressed neatly, hence they are used only for economical 

 reasons in the absence of tetter local materials. 



The Lafayette and Columbia formations contain occasional ledges of 

 ferruginous sandstones and conglomerates that have furnished a poor 

 grade of building stone for foundation purposes. 



PEAT. 



The term peat is applied to a dark-colored nearly black deposit formed 

 by the accumulation and slow decay of vegetable matter under water in 

 bogs and swamps. It is composed chiefiy of partly decomposed and dis- 

 integrated vegetable matter. When impure and containing too much 

 mineral matter to burn freely the black swamp deposits are more properly 



