QUARRIES IN KNOX COUNTY. 
123 
depth of about 17 feet. The drainage requires pumping. The strip- 
ping is insignificant, but in places is from 5 to 10 feet thick. 
Rock structure : The sheets, which are from 2 to 14 feet thick, are 
lenticular, tapering, and curve over to the northwest and southeast at 
low angles. (See PL VIII, A.) Joint courses are shown in fig. 
22. System A is prominent and forms a heading on the south side of 
the island, shown in PL VIII, ^4. B dips 40° SE., occurs but occa- 
sionally, and is discontinuous. C also forms a heading. I) dips 65° 
SW. and is also prominent. The rift is vertical, with east- west 
course. Irregular horizontal dikes of pegmatite, up to 2 inches thick, 
consist of the same minerals as the granite — a pink orthoclase and 
microcline, smoky quartz, cream-colored oligoclase, and biotite. Sap 
occurs along the sheets and joints A and C, and markedly at the sur- 
face in places up to a foot in thickness. (For details see p. 53 and 
Fig. 22. — Structure at High Isle quarry, Knox County. 
fig. 2.) Along some of the headings of A the granite is weathered 
to a sand at a depth of 20 feet. 
The plant consists of 9 derricks, worked by 8 engines ; 2 locomotive 
cranes, 2 compressors (with a capacity of 862 cubic feet per minute), 
15 large pneumatic drills, 28 pneumatic plug drills, 13 surfacers, and 
20 pneumatic hand tools. 
Transportation is effected by gravity and track 650 feet to wharf. 
The product is used for buildings, chiefly in Philadelphia. Sundry 
small buildings and bridge seats for the Pennsylvania Railroad have 
been made of this stone. Contract in 1905: The new Wanamaker 
store in Philadelphia. 
Dix Island quarries, Muscle Ridge Plantation, one-half mile south- 
west of High Isle. Owner, Thomas Dwyer, 1613 Amsterdam avenue, 
New York. 
Six openings were operated extensively in 1880 by the Dix Island 
