330 The OrUjinal Cha:y Rochs — Brainerd and SeeJij. 
exposed in each of the three areas. Just east of the street 
along section IV. all the strata are to be seen, although in a 
limited area. Forty rods farther south on the north-east bank 
of the river, they are found resting on the mottled rocks of 
Group B, 5. But half a mile farther south they appear in a 
long ridge with beautiful sections of Marchisonia and Ortho- 
ceras weathered on the surface. There is reason to suspect that 
rocks of this horizon occur in even greater force along the 
eastern shores of lake Champlain, and they remind one of 
similar strata described by Sir Wm. Logan as occurring at the 
Mingan island. (See Greology of Canada, p. 135.) 
Along section IV, in the village of Chazy, overlying the one 
foot stratum of tough dolomite, (C, 7) are to be seen the lower 
beds of Rhynchonella, above thirty-six feet in thickness. 
These pass into lighter colored and more massive beds of purer 
limestone, which appear just north of a large barn, in a low 
ledge sloping eastvf ard into the soil of a garden, that conceals 
all the higher strata of Group C. But in the bed of the Chazy 
River, forty rods to the north just under the dam, thd light-grey 
strata again appear, and are succeeded by other strata of Rhyn- 
chonella at least thirty-two feet in thickness. These three 
measures, amounting in all to ninety-five feet, should be classed 
together, the difference resulting chiefly from the greater or 
less degree of earthy matter in the matrix surrounding the 
shells. The shells themselves contain pure calcspar, and occa- 
sionally small crystals of quartz; though some are partly 
hollow, like miniature geodes. These strata crop out in the 
central and western areas, usually in rounded ledges, the rock 
often disintegrating after long exposure. We may here note 
that the thickness of the Rh3aichonella beds in Grande Isle 
C©., Vt., were found to be seventy-one feet. 
There yet remain about forty feet of rock before we reach 
the lowest observed strata of the Black River or Birdseye for- 
mation. Unfortunately this is everywhere concealed by the 
soil, excepting about eight feet which are scantily exposed in the 
bed of the river. This is a tough, bh^k dolomitic rock. The 
horizon, however, is one of special interest, corresponding to 
the strata of Fort Ciissin, Vt., in whicli in 1886 over thirty new 
species were discovered. (See Bull. Am. Museum of Nat. 
History, vol. 1. No. 8.) 
Mid'dJehiiry College. 
