ERIE DIVISION. 
319 
nearly parallel to the Hudson, to opposite Saugerties ; thence around the Catskills, to the 
mountains east of Rensselaerville ; and thence westward through Schoharie county, a dis¬ 
tance of about one hundred and forty miles, without reckoning the winding line of outcrop, 
in consequence of various irregularities of the ground. 
The flag-stone rock, like many others of this series that do not disintegrate by exposure to 
the weather, frequently forms terraces; and in many places it is but slightly covered by soil, 
or by a thin stratum of rock which is similar to this, except that it does not split as regularly. 
The quarrymen select such places as present the least obstruction to working, and are nearest 
to good, roads leading to the Hudson river. The strata lie nearly horizontal, pitching very 
slightly to the northwest from the Delaware to Woodstock,* then westward to east of Rensse¬ 
laerville, then southwestward and southward to Summit in Schoharie county. 
The flag-stone stratum was seen in many places in Albany and Greene counties, where it 
has not been worked. This stratum has been, and is still, extensively worked for flagging stone 
in Coeymans in Albany county. This stone is not confined to the hills in which it is quarried, 
as is generally imagined by the people there, notwithstanding the numerous facts continually 
presented to eyes that do not see ; but this, as well as each of the other particular strata, 
occupies a uniform and determinate position, and by careful examination can be found, and 
opened in every hill along its range that is high enough to be intersected by its plane. The 
quantity of this rock is so great that it cannot be exhausted. It has been traced, exclusive 
of the sinuosities produced by valleys intersecting its plane, a distance of one hundred and 
forty miles in the First geological district, and it undoubtedly underlies all the country that 
is occupied by that portion of the Catskill and Erie divisions that overlie this rock. The 
principal flag-stone quarries in Coeymans are those of Mr. William Briggs and Mr. C. 
Brown. 
A bed of blue crumbly soft shale underlies many of the flag-stone quarries, and slaty grits 
with water lined laminje of deposition overlie, where all the strata occur together. Remains 
of plants, apparently of terrene plants, sometimes carbonized, sometimes pyritized, and 
sometimes as mere impressions, are common in the strata immediately overlying the flag¬ 
stone stratum, and are found also in the flag-stone. One fossil seems to be peculiar to the flag¬ 
stone stratum. It seems too indistinct for determination, but is cylindrical in form, of about 
the diameter of a pipe stem or a quill, lying in graceful curves which frequently intersect, 
sometimes like a flattened helix. They may be seen occasionally in the flag-stones from the 
quarries in Ulster, Greene and Albany counties, that are laid for side-walks in Albany, New- 
York, and various towns where they have been used. My attention was first called to these 
curious markings by Prof. L. D. Gale, before the commencement of the geological survey 
of New-York. 
The Erie division of rocks is included in the section from the South mountain, near the 
Mountain House, to the stone bridge of the Kaaterskill,* between 128 and 134. 
• From the Delaware to Wawarsiiig, the strata next the valley of the Delaware and Hudson canal are all upturned at a higfc 
angle, and a flag-stone stratum throughout this distance is upheaved in the same way as the adjacent rocks. 
