Ors 
Prime. | 252 [Dec. 21; 
feet in thickness, and then a break in continuity have occurred, to be suc- 
ceeded by another layer of the same material ? 
While the greater portion of the limestone has in all probability been 
formed in deep water, we have one instance in a quarry in Uhlersville on 
the Delaware where it must have been formed as a beach, since we find 
here distinct traces of ripple marks along the entire face of the quarry, 
some sixty feet high and fifty feet deep, the strata being tilted nearly 
vertically. 
It has been generally supposed that the limestone dips almost universally 
southward ; and while this view holds good for Northampton county, ex- 
cept at the junction of No. IT with the No. III slates and along the north 
flank of the South Mountains, it is not the case in Lehigh county ; for here 
we find north-west dips, more especially along an axis which is prolonged 
Some distance into Northampton county, ashort distance above Catasauqua. 
As a general thing the limestones pass conformably under the No. III 
slates, and the few exceptions where the slates dip towards the lime- 
stones, and the latter away from the slates can readily be explained by an 
overturning of the beds towards the south, by which means as in the slate 
quarry close to and south of Ironton the slate apparently passes conform- 
ably below the limestone. 
Overlying the No. II limestone occurs the Trenton limestone which is 
more fossiliferous and contains such characteristic fossils as Chetetes lyco- 
perdon and Orthis pectinella as well as the stems of an encrinite. It was 
first found about a mile south of Ironton in Lehigh county, then at inter- 
vals between Bath and Martins Creek in Northampton county ; but all 
attempts to trace it as a continuous formation have thus far been unsuccess- 
ful owing to the lack of outcrops. It occurs most extensively at Martins 
Creek on the Delaware, at a point a little south of the cotton mill, and is 
there as elsewhere apparently conformable with the underlying Magnesian 
limestone. : 
This limestone resembles in appearance the No. II, being however 
more compact and not at all crystalline and of a gray black color. 
There has been no apparent sudden break between the two, but the 
transition has been a gradual one. This was to be expected if the sub- 
sidence of the sea-bottom was steady and slow. An examination of the 
beds between Ironton in Lehigh county and the Delaware River, as close 
to the junction of the limestone and slate as possible, has shown that the 
limestone for the entire distance is more or less of a hydraulic one, due to 
the greater proportion of alumina which it contains. This also was to be 
expected if the subsidence continued. as signalling an approach to the era 
of slate-formation and open sea deposition. - These limestones are utilized 
on the Lehigh river in the manufacture of hydraulic cements and lately 
Portland cement has been made at the Copley Cement Works, which is 
said to be nearly or quite equal to the imported. Careful search and the 
demand for it will no doubt cause this variety of the limestone to be ex- 
plored at various other points in the two counties, and will in time render 
us independent of the cement now sent from the Hudson River, The lime- 
