3(32 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
ing currents, while the slate is the finer off-shore material powerfully 
compressed and largely altered to mica. 
The chief difficulty attending the Slatington slate industry is the 
complex structure of the slate beds. The frequency of the grit beds, 
"rock" or " ribbon " of the quarrymen, is one element in this. Then 
the folds vary greatly in width. One limb of a trough (syncline) may 
measure over 200 feet at the horizon or the arch (anticline) maybe so 
sharp as to measure scarcely 25 feet across. These folds are more or 
less overturned, so that the ribbon intersects the cleavage at different 
angles on the sides of the fold, thus differently determining the size 
of the slate blocks and to some extent the quality of the slate. The 
axes of these overturned folds pitch alternately east -southeast and 
west-northwest at from 5° to 10° or bend 10° laterally, i. e., north- 
south. The folds have all been truncated at the surface by erosion, 
so that it is difficult to trace any one bed across the strike. The 
rock surface may be but a few inches below the turf or may be 
buried beneath 30 to 40 feet of glacial deposits. There is frequently 
a flexure of the cleavage ("curl") for a few inches near the ribbon; 
more rarely there is a curvature of the cleavage across the entire bed. 
Slates cut from such beds are called "bents," and are used for cov- 
ering curved or conical roofs. At the old Hughes quarry this curva- 
ture in 25 feet along the dip of the cleavage amounts to a change of 
20° in the dip, the dip at the top being 45°, but 05° below. Exception- 
ally the joints, instead of crossing bedding and cleavage at a certain 
angle, undulate like bedding planes. Faulting seems to occur rarely. 
It would seem that nothing less than an exhaustive study of the 
stratigraphy of the region with the aid of a perfectly reliable large- 
scale topographic map would suffice to furnish a safe basis for 
such an industry, but in fact the industry has attained its present 
prosperity without such aid, and it is even doubtful whether a 
pocket compass could be found on the person of any foreman in the 
quarries. In view of the very small collective area of all the open- 
ings about Slatington compared to the extent of the slate beds as 
shown by the location of these openings, and in view also of the finan- 
cial risks growing out of the difficult st rat tgraphy, it is surprising that 
the diamond drill, used so effectively in marble and other regions, has 
not been brought into requisition here also. The core from such a 
drill would not only show the quality of the slate but its thickness, 
in many cases, as well as the dip of the cleavage and ribbon. A 
less costly drill, which secures a core by the rotation of a wrought-iron 
pipe upon steel shot, has been successfully used in the Vermont slate 
belt. 
Attention ought to be called to certain outcrops of dark reddish 
shales a mile southeast and southwest of Werleys Corners in Weisen- 
berg, or about 1-0 miles southwest of Slatington. A microscopic exam- 
ination of a surface specimen from the first of these places shows it to 
