182 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
The Hawaiian System of Volcanoes. 
A double line of volcanoes like the Hawaiian does not necessarily 
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imply that there must exist two great parallel fissures in the earth’s 
crust. A sin ode great torsion crack with the attendant fringe of 
border-fractures in the superficial layer of the crust, or simple frac¬ 
turing in accordance with this structure will account for all the phe¬ 
nomena of distribution of volcanoes in couplets along a double line. 
The commonly accepted view of two parallel fissures fails to account 
for the occurrence of the volcanoes in couplets and for the interval 
between them. The b-plane ranges are characteristic of the Pacific 
volcanic area. Wherever c-fractures pass between these b-planes, at 
the point of intersection there will be found an axis of maximum weak¬ 
ness opening downward, and along this path the lavas may escape. 
(See Plate 2 , fig. 12.) The matching of this fracture system to the 
rents in the Hawaiian group is shown on Plate 3 , fig 2. It should 
be noted that the system as displayed on a small scale, calls for regu¬ 
larity of interval between b-planes, and makes the point of greatest 
weakness where the c-fractures end against the b-planes. There is 
a very marked agreement with the system in the case of the 
Hawaiian group. 
Faults. 
A comparison with systems of faults, in the case of the Juratrias 
area of Connecticut worked out by Davis, suggests an analogy with 
the cross-fractures of joints, but it does not seem possible at present 
to connect these structures causally. 
