32 W. M. Fontaine—Mesozoic Strata of Virginia. 
mal ones. The most common matrix enclosing the stones is 
red shal 
The most important, and by far the longest uninterrupted bed 
of stones, is that known under the name of the “ Potomac Mar- 
ble,” or the “Limestone Breccia.” This enters the State near 
Point of Rocks, Maryland. At Point of Rocks it is well ex- 
posed by the — for the Metropolitan Branch of the Balti- 
more and Ohio Railroad. I examined the deposit at this place 
oniaares's to determine the character and origin of the stones. 
stones here are all limestone. After long and careful search 
I foaud only one fragment not limestone. This was a slab about — 
eighteen inches wide and four inches thick, of apparently Pots: — 
dam sandstone. In this vicinity the Azoic rocks are mica 
slates. Azoic limestone occurs some distance to the northeast, 
and may have furnished an impure pinkish limestone, which — 
ranks third in the abundance and size of the fragments it has 
afforded. These are rarely over six inches in diameter and — 
sometimes a foot in Parser — stones are when hel ! 
constantly diminishing amount of limestone. As this limestone 
must have come from Maryland and Pennsylvania, we see that 
some of — ina must have traveled long distances, viz: forty 
or fifty mi The predominance of limestone is marked for 
bur i 
some 5, ones south of 
A second deposit, not caneriall with the last, is well shown q 
near Gnipepper er Court House, where I made a careful examina ~ 
A One een EE ILS Ric eget at vee ay oe a Ae ere a 
