212 
LACCOLITHIC GENESIS 
eminences gives rise to the suspicion that all of their story is not 
yet told. 
Recapitulation 
From the foregoing account it appears that: 
(1.) The simple Blister Hypothesis of laccolithic formation 
is entirely untenable; 
(2.) No laccoliths are probably regular lenticular masses 
haphazardly disposed; 
(3.) Unaided hydrostatic pressure alone is rarely, if ever, 
competent to produce notable interstratal swelling and filling by 
normal magmas; 
(4.) The type form of laccolithic mass is an asymmetric or 
wedge-shaped body; 
(5.) The super-intrusive load is severely limited to a very 
moderate columnar section, perhaps never exceeding 3000 feet 
of strata; 
(6.) Laccolithic intrusion is genetically associated with pro¬ 
found crustal rupture and displacement; 
(7.) The initial impetus to laccolithic formation is a release 
from orographic strain involved in local folding whereby the 
load of superincumbent rocks is, potentially at least, maintained 
by the rigidity of beds comprising an arch; 
(8.) The tenor of magmatic viscosity is doubtless a very ap¬ 
preciable and perhaps measurable factor in the production of 
laccolithic bodies; 
(9.) Laccoliths are not in any sense merely thickened sills 
or transformed dykes, but owe their especial expression to en¬ 
tirely distinct and widely different tectonic conditions; 
(10.) The formation of laccoliths is a necessary consequence 
of a combination of several unrelated conditions and circum¬ 
stances operating successively or in conjunction. 
