"iceland RRO RES 
; 
Geology, §c. of the Connecticut. 35 
9. ARGILLITE. 
Colored Brick Red. 
The remarks last made in regard to the primitive green- 
stone, chlorite slate, &c. will apply to this rock. For we find 
it near the two terminations of the secondary tract and on the 
—_ of it-viz. in Woodbridge at the south end, and com- 
on the north at Leyden and extending at least as 
fa rae ae Vermont. The northern deposite is 
much the most extensive and is best characterized. In both 
places, however, it is often tortuous and slightly undulating, 
especially when passing into mica slate. It embraces nu- 
merous beds and “tuberculous masses” of white quartz— 
perhaps the milky quartz. The ae into mica slate is 
usually very — the characters of the argillite losing 
themselves by imperceptil e char nges- in those of the 
mica slate, so thi for a consider nee, the observer 
may be in doubt to which rock to volt the aggregate. The 
Woodbridge woe occasionally alternates with mica slate, 
(Journal Sci. Vol. 2. p. 203.) and I have ascertained that 
this is the case also with that of Vermont. That which is 
just beginning to pass into mica slate, alternates also with a 
peculiar coarse limestone to be described under the next ar- 
ticle; or rather, - limestone: forms beds in the argillite— 
for instance in ney. 
Wee prine ‘ipal Shere in éxtending the map so much beyond 
secondary region on the north, was to include all the 
mail llite to be found along the Connecticut. Whether I have 
ected this object I am not certain. The Rev. E. D. 
Andrews, who communicated to me several facts on this 
subject, is of opinion that the northern limit of the argillite 
is on the south side of Williams’ river in Rockingham, three 
miles north of Bellows Falls; but he had not examined the 
regions beyond with sufficient care to decide the point _ 
certain 
In Guilford, Vermont, this argillite alternates with a pecu- 
liar rock which Professor Dewey remarks appears “ to be 
a talco-argillite with much quartz.””. Its stratification is less 
perfect than the argillite ; or, rather, it has more of the ir- 
regularities and tortuosities of mica mates Its small extent 
