626 GEOLOGY OF OHIO. 
fossil shells and fishes, and are not only wholly free from any markings 
that would indicate origin in shallow water, but could only have been’ 
accumulated at considerable distance from the shores. That the change 
was suddenly accomplished is evident from the very abrupt boundary - 
that obtains between the quarry courses and the black slate. The upper 
boundary of the slate is equally well marked. The conditions under 
which this deposit was formed were evidently very nearly like those to 
which the Huron shales owe their origin, and were in marked contrast 
with both those that immediately precede and immediately follow them. 
Contrary to what might be expected, this slate proves to be quite re- 
fractory when exposed to heat, if the heat be applied carefully at first. 
It has in this way acquired a local reputation as a firestone, and is used 
for chimney jambs and other similar purposes. 
4, The next division in ascending order has for its chief character- 
istic the well-known and very valuable quarries of the Waverly system 
that lie along the Ohio River below Portsmouth. This subdivision has a 
definite base, viz., the upper surface of the Waverly black slate; but 
there is no characteristic stratum that constitutes a convenient superior 
limit. As the most valuable of the building rock, however, that is fur- 
nished by this part of the series in southern Ohio occurs within fifty feet 
of the slate, these fifty feet next above the slate may be somewhat arbi- 
trarily taken as a subdivision. It may be designated as the Buena Vista 
section—the name being derived from a locality on the Ohio River that 
furnishes a large amount of stone of unequaled quality. This division is 
very well represented in Pike county, and some of the most valuable build- 
ing stone of the Scioto valley belongs to it. The Buena Vista quarries, as 
is stated by Prof. Andrews in the Preliminary Report of the Ohio Geologi- 
cal Survey for 1869, immediately overlie the Waverly black slate. There 
is a series of beds sometimes exactly corresponding to this: in geological 
position, and sometimes separated from the slate by a few intervening 
feet of shale or clay, but which agree so closely with each other in physi- 
cal characteristics as to make their identity probable. The courses of 
stone that are exposed at the Tar Spring have already been referred to. 
Occupying, as they do, the position of the Buena Vista stone, and con- 
sisting, like it, of massive layers, the identification of them with the 
above named quarries will hardly be questioned. The color of these 
beds, however, in all exposed portions, is brownish yellow. In a very 
promising quarry opened near the summit of a hill south-east of the vil- 
lage of Latham, a heavy ledge—belonging certainly very near to this hori- 
zon—agrees quite well, both in color and texture, with the Buena Vista 
stone. The great extent of the true Waverly quarries in all this portion 
