82 
THE GRANITES OF MAINE. 
10 feet thick, consisting of two large aplite dikes that have a north- 
south course. The drainage is natural. There are from G inches to 
3 feet of loam on the granite surface, but in places it is bare. 
Kbck structure : In the center of the lower quarry there is a lami- 
nation in folds 20 feet broad and 3 feet high, occasioned by the paral- 
lelism and abundance of biotite plates along certain planes. Some of 
these planes show evidence of friction along them. There is also a 
north-south vertical structure associated with the dikes of aplite 
between the two quarries. The sheets range from 4 inches to G feet in 
Fig. ti. —Structure ;it .Maine and New Hatapshire Granite Company's quarry at North -lay. 
thickness. In the upper 25 feet the sheets are thin, but below thai they 
become gradually thicker. In cross section they feather out alternately, 
or "toe in," as described on page 35. At the top of the hill and at 
the east side of the upper quarry they arc horizontal, but on the west 
side they curve over westward, dipping 5°-10°, and possibly a little 
more in the lower quarry, governing the slope of the hill. At the 
north side of the lower quarry i- a heading striking X. 50°-G0° E., 
dipping G0° and also 90°. The courses of the various joint systems 
and dikes are shown in fig. G. Of joints B there are four discontin- 
uous ones in a space of 50 feet in the upper quarry. The rift is 
horizontal and there is no grain. The pegmatite dikes consist of 
milk-white potash (microcline) and soda-lime (oligoclase) feldspar, 
smoky quartz, biotite, and muscovite, and measure up to 2 feet G 
inches. Knots are exceptional and measure up to 12 inches across. 
Heading A is covered with limonite from oxidation of pyrite. Fer- 
ruginous discoloration (sap) is noticeably absent from the sheets. 
The plant consists of 8 power and 2 hand derricks, 8 engines, 2 
locomotive cranes, 1 compressor (capacity, 7G2 cubic feet per min- 
ute), 4 steam or air drills, 8 pneumatic plug drills, 2 surfacers, 14 
