188 
THE (lliAMTKS OK AIAIXK. 
Rock structure: The sheets, from 3 to 20 feet thick, curve over on 
both the north and the south side of the ridge, with a dip of not less 
than 10°. Seen from the western spur of the island, two 20-foot 
sheets form the upper part of the hill ; beneath these, however, is! 
a much thicker sheet, which at the east-southeast end of the hill and 
quarry measures fully 60 feet — too thick for economic working. 
These sheets are shown in PL IV, .1. as seen looking northwest. 
This abnormally thick sheet is referred to by Merrill. The sheets 
are traversed by three sets of joints, as shown in figure 27. A" 
dips 50 c to 55° \\\: B is vertical, and C, which is diagonal to A and B, 
dips 40 NE. The rift is vertical, with X. 85° E. course. The east- 
west system (B), which is parallel to the rift, reappears on Heron 
Neck, as shown in PI. II. .1. B and C are both shown on PI. IV, A. 
FlG 
Structure at Hurricane Island quarry, Kn<>\ County. 
The B surface- are, in places, coated with epidote. Occasional knot 
occur. 
The plant consists of s derricks, run by 5 engines; 2 traveling steair 
cranes. 1 compressor (with capacity of 900 cubic feet of air pet 
minute). 1 channeler, 6 steam drill-. 23 pneumatic plug drills, 7 sur 
facer-. .") polishing lathe- c2 -mall and 3 for stones, 30 feet by 5 feet) 
1 steel saw for sawing granite with chilled iron shot, 32 pneumati< 
hand tools, and -J -team pumps. 
Transportation is effected by track, -lot) feet long, to dock. 
The product is used for buildings and monuments. The wast 
goes into paving blocks. The chief markets are New York, Phi la 
delphia, and the interior. Specimen buildings: The Suffolk Count; 
court-house at Boston; the St. Louis post-office and custom-house 
two building- for the Naval Academy at Annapolis, Md. 
"Ann. Rept. Smithsonian Inst., pt. 2, 1889, p. U5. 
