It will be proper to notice in this place, a petrifaction of wood which is found on the road from Washington to Fredericksburgh, 16 miles from the latter, and four miles north of the court-house in Stafford county. It is remarkable for its size, rather than for any singularity in the composition. It was found by digging away the earth on the side of the road, and appears to have been the trunk of a considerable tree. It is firmly fixed in the ground, and penetrates it obliquely; how far has not yet been ascertained. At the time I saw it about two feet had been exposed. The diameter is about eight inches. Its colour is white, sometimes resembling that of wood. The fibres are well preserved, and so is the general structure. It is much to be desired, that some one would clear it from its bed, and give it entire to one of our mineralogical cabinets. _Geological Features._ Next to the alluvial and secondary formations, as you pass to the west and northwest, are to be found ranges of granite and shistose, and other primitive rocks; interspersed with these may be seen sandstone, clay, slate, quartz, and limestone. Granite ranges were particularly seen in the neighbourhood of Fredericksburgh, crossing the Rappahannock; and in Orange and Albemarle counties, extending nearly to the Blue Ridge. Great quantities of quartz and quartz rock, sometimes covering with their fragments the sides of hills, are frequent. Another, and more interesting rock in the same connexion, is found in Albemarle county. For some time I doubted to what class to refer it. But from its resemblance to the rocks of the east and west mountains near New-Haven, I ventured to call it trap or whinstone. It becomes more abundant as you approach the Blue Ridge, and the granite disappears. On the sides and summit of the mountain, its appearance is more decidedly that of greenstone. In crossing the southwest mountain, the range to which Monticello belongs, and distant from the Blue Ridge about 25 miles, I observed the same rock. Whether this opinion is just, you will be able to decide from the specimens which have been forwarded. _Blue Ridge._