242 Additional Remarks on the 
Between the range of mica-slate and the Hudson, the 
the same rocks are found, as have been already described 
in the counties of Columbia and Rensselaer, Vol. VIII. pp. 
2i—24. After passing the range of mica-slate, we find 
transition limestone, transition argillite, gray wacke, and 
the argillite along the Hudson. In this part of Dutchess 
inty, the transition limestone presents generally s 
e characters as in the two counties north of it. 
masses, however, which contained many fragments of ar- 
gillite, aeienenrure: the age of the rock very clearly. The 
lies the west base of the highlands in the 
south part of this county. It appears to be associated 
with gneiss on the east; while on the west it is, as before 
stated, connected with transition argillite. It appears also 
in beds i in the argillite. 
_Gray-wacke appears to be less abundant in Dutchess co. 
than i oe Columbia co. It occurs however in masses over 
much of the western half of the county. In the town rat 
Washington is a huge ledge of it, composed evel of 
quartz cemented by an argillaceous substance. Speci- 
mens, similar to thee, are found in the gray-wacke, E. of 
Troy, but I had never seen such an extensive mass of this 
variety. 
Transition argillite is the principal rock in Dutchess co. 
west of the mica-slate. Although it sometimes contains 
limestone and gray-wacke, or alternates with them, it is es- 
sentially the same rock where it first appears and where 
it forms the banks of the Hudson—full of seams and easily 
broken into angular fragments. In the town of Fishkill, ! 
noticed several beds of gray-wacke so disposed in it as to 
show that the origin of the two rocks must have been co- 
temporaneous. The argillite and gray-wacke in New- 
burgh, —- to Fishkill, contain petrifactions of several 
kinds. Some masses of gray-wacke are compose 
wholly of Fecibiatalites while in others, there are e frag- 
ments of argillite, siliceous slate, &c., like those of the 
same rock at Troy. In Fishkill too I found petrifactions 
in siliceous slate, like those at Hudson, associated with ar- 
—— range of mica-slate, before mentioned, seems te 
have a small inclination to the direction of the sree 
themselves. The hills, which constitute the range, 
