As others have described more minutely and accurately than I can, the country north of Virginia, I shall begin with a few remarks on the geological character of that State. It is there that the traveller, in passing from the Atlantic to the interior, crosses successively the most important formations of the earth, from the most recent alluvial to the oldest primitive. For a considerable distance from the coast, the country is alluvial. It then assumes an older secondary formation[30]--and sandstone and puddingstone are frequent. This is the character of the District of Columbia, and indeed of a great part of the valley of the Potomac. _Sandstone of the Capitol, &c._ In this valley, and adjacent to the river, is found the _sandstone_ of which the President's house, and the Capitol are constructed. It is composed of fine silicious grains, is easily wrought, and from its colour, has the appearance at a small distance of white marble. _Beautiful Breccia._ It is also in the valley of this river, and not far from its famous passage through the Blue Ridge, that immense quarries of beautiful Breccia have been opened. This rock was first brought into use by Mr. Latrobe, for some years employed by the government as principal architect. It is composed of pebbles, and fragments of silicious and calcareous stones of almost every size, from a grain, to several inches in diameter, strongly and perfectly cemented. Some are angular, others rounded. Their colours are very various, and often bright. Red, white, brown, gray, and green, are alternately conspicuous, with every intermediate shade. Owing to the silicious stones which are frequently imbedded through the mass, it is wrought with much difficulty; but when finished, shows a fine polish, and is unquestionably one of the most beautifully variegated marbles, that ever ornamented any place. It would be difficult to conceive of any thing more grand than the hall of the Representatives, in the Capitol, supported as it is by twenty or thirty pillars formed of the solid rock, and placed in an amphitheatrical range; each pillar about three feet in diameter, and twenty in height. Some idea of the labour which is employed in working the marble may be formed from the fact, that the expense of each pillar is estimated at five thousand dollars. The specimens in your possession, are good examples of its general structure, but convey no adequate idea of its beauty. _Petrifaction of Wood._