544 EH. W. Hilgard on Mallet’s Theory of Vulcanicity. 
ascribing precisely these most extensive fissure eruptions in 
the world to the “ineffectual fires” of the volcanic period, aris- 
ing alone from transformed motion. 
Indeed, it is not easy to understand the precise mechanism 
of the great fissure eruptions as a consequence of nucleal con- 
ay 
in the crust (whether of form, thickness or density), and thus 
act as a vis-a-lergo. 
t first blush, the “squeezing out of sub-mountain liquid 
matter,” assumed by LeConte as the consequence of the folding 
and fissuring of strata by tangenti 
dence of steady static outflow, and regular upbuilding, is espe- 
cially cogent; and as LeConte remarks, it has been slow work 
—as, indeed, is usually or universally the case with mountain 
building.* . 
The assumption of locally limited fire seas with a solid 
globe, as made by Danat+ in conformity with Hopkins’s views, 
would remove the difficulty, if the crust could be assum 
as contracting, on the whole, independently of the portions over 
e 
eus solidified by pressure, OF 
whether all within the crust is actually liquid. 
LeConte says (loc. cit., p. 179) that the outsqueezing of the liquid has 
izontal pre ed 
traction of the whole earth;” and then (p. 180) that “ whether by uplifting or 0 
building, the actual increase of height would be precisely the same, being g 
mined by the amount of lateral ing,” he seems to thi f crust-contraction 
nucleus too large for it, rather than of Mallet’s “freely descending” crust. 
Or, if he = result of motion rs too 
see on what ground a “ wplifting” could be consi: e 
equi t of an uption of liquid rock In either case 
Sates : oS er ing of 
the lifting done would be the same; but what of the enormous heat of ? si 
: i of the Results of the Earth’s Contraction, this Jour., Aug., 1873, P- ! 
 ¥ Ibid, July, 1873, p. 7 and ff 
