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/ 
systems. It is a curious fact, however, that of the ten possible 
intersections of the dikes of these two systems on or near Gun 
Rock, only this one is actually exposed above the water. 
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— e 7 
FIG. 14.— PLAN SHOWING THE INTERSECTION OF DIKES ON 
THE SHORE, EAST OF GuN Rock, AND THE ENCLOSED 
FRAGMENTS IN DIKES II AND 12. SCALE, I INCH ==25 FEET. 
The next dike in regular order is the continuation of 3 of the 
first system, and the exposure is perfect from one side of the 
promontory to the other. About 40 feet north of this dike, 
and parallel with it in strike and hade, is an interesting quartz 
vein one inch or a little more in width. . It is perfectly straight 
and continuous, its outcrop dividing the entire mass of Gun 
Rock by one sharply-defined white line. Dike 12 of the second 
system is about 120 feet north of 11; and nearly 20 feet 
farther north is 13, a parallel and much smaller dike. Dike 13 
is closely parallel to 11, appearing just to clear the extremity of 
the ledge east of Gun Rock and to be continued in a similar dike 
(13) on Green Hill Ledge. But dike 12 takes a more diagonal 
course, being, on the eastern ledge, 100 feet from 13 and only 
42 feet from 11. The large dike (12) is, perhaps, the most 
