Geological and Mineralogical JYotices. 231 



is engulphed in some fissures in the rock, and at a distance of two 

 hundred yards issues again at the base of a small ledge and finds its 

 way in an open and shorter current to Black river. The channel 

 below this fissure is therefore perfectly dry. The rock in the wood 

 near by, is cavernous, as indicated by the subterraneous passage of 

 the river — by several small accessible caverns, with roof and sides 

 formed of large confusedly congregated masses, and by a rumbling 

 noise when a carriage is driven over the road — the structure of this 

 part indicating the effect of a powerful disruptive agency. 



In the dry bed of the stream the rock has a different aspect in seve- 

 ral particulars from the superior strata as found in the cliffs — the fossils 

 are madreporites, corallines, and orlhocerse, in great number, and the 

 latter of large size imbedded and their upper half abraded by the cur- 

 rent, but their septa, as usual, harder than their gangue, still project- 

 ing above its surface. These are from two to three feet in length j the 

 siphunculus filled with calc spar, and the whole in some cases mineral- 

 ized, as it were, by a hard, black limestone, with a conchoidal fracture. 



All attempts to detach a complete specimen were futile, but my 

 search was rewarded by finding loose the smaller termination of an 

 orthocera, perfect in its external form — septa oblique to its axis — 

 about eight inches long — diameters at the upper end five inches and 

 three inches and a half — and circumference twelve inches and a halfj 

 and if the entire length were in proportion to these dimensions, com- 

 pared with the specimens above cited, this one must have been many 

 feet long. 



The strata here are much thicker than those in the upper series, 

 and the bed of the stream in its whole width, and for a quarter of a 

 mile, is divided at various distances apart, by several parallel longi- 

 tudinal fissures, which are not vertical, but have a considerable dip 

 to the east and a direction as nearly as I could judge without a nee- 

 dle, N. by W. and S. by E. Obliquely these are intersected by 

 other similar fissures — direction nearly N. E. and S. W., and dip 

 S. E. nearly. The intersection of these, of course divides the rock 

 into rhomboidal blocks, having a double inclination, whose sides are 

 oblique angled parallelograms, and each opposite pair equal and 

 similar. With two straight edged sticks, the only means at hand, I 

 attempted, with the assistance of a friend, to measure the angles of 

 intersection of the fissures, which were transferred carefully to paper 

 with the pencil, viz. a. 67^°, 6. 111^°= 179°; c. 107^°, d. 72° = 

 179i°. Allowing for error in measurement of half a degree, we 

 have the following result — to a. and b. and c. add half a degree, and 



