Fossil Wood and Lu/iiifes Krwitlton. K).l 
after which there was a gradual uplifting of the land. This 
newly emerged land was now subjected to the powerful action 
of moving water which cut down and transported a large por- 
tion of it, leaving now and then those irregular or lenticular 
masses intact which were eventually surrounded and covered by 
a lighter material and the whole was tinally buried under the 
Tertiary. 
Good exposures of this formation, containing lignite and 
silicified wood, occur at Fort Washington, White House Land- 
ing and Acquia Creek on the Potomac: at Dutch Gap and vicinity 
on the James river; and also in the cities of Washington and 
Baltimore where excavations have been made. Cuts along the 
lines of rail-ways which pass through this formation often give 
good sections. Most of the material upon which the following 
observations are based, came from these localities . 
The wood of this formation occurs under two widely different 
conditions, viz: as lignite and as silicified wood. There seems 
to be almost no transition between the two forms, although in 
one instance, in a silicified specimen from the new reservoir,. 
Washington, a few small liguitized areas were detected. There 
is reason for supposing, however, that some of the silicified 
forms are also represented in a lignitized state; that is, owing 
to different conditions of fossilization some specimens of a 
species w^ere silicified, while others were turned to lignite. 
The lignite is much more abundant than the silicified form, 
occurring in the above mentioned lenticular masses in pieces of 
considerable size and in the loose surrounding material as 
minute fragments, which shows that this latter is the result of 
the wearing away of a large part of the original deposit. One 
of the largest specimens noted was found at Fort Washington. 
This was a log about five feet in length, eight inches in \vidth, 
and four in thickness. A cross section of this specimen, of 
course, would have been lenticular, showing that it had been 
subjected to great horizontal pressure. A transverse section as 
seen under the microscope shows the c*!lls completely collapsed 
and distorted by the pressure. 
In color this lignite is almost unifor)nly jet black, in only a 
few cases being of a slightly brownish cast. It has a specific 
gravity of about 1.333, and breaks with a true conchoidal frac- 
ture like ordinary anthriicite. When thus broken it does not 
