Geological Results of the Earth’s Contraction. 91 
the tension causing fractures would be exerted with some reference to 
the structural lines, the tension and the structure being both a simulta- 
neous consequence of cooling, (iii, 894.) 
Direction of fissures modified by the relative positions of the large 
areas of unequal contraction, and whatever the actual course, frequently 
attended by transverse fractures, (iii, 395, 396. 
. As the force of tension acts tangentially in a great degree, (like 
the pressure of stone against stone in an arch, and that of the whole 
arch against the supporting or confining abutments,) the effects will ap- 
pear either over the subsiding area, or on its borders; and they will be 
confined to the latter position whenever the surface is strong enough to 
resist fracture, (iii, 96, 97, 181, 395.) i dighege 
_ d. The borders of large subsiding areas sooner or later experiencing 
deep fissurings and extensive upliftings through the tension or horizontal 
orce of the subsiding crust; these upliftings frequently in parallel se- 
ries, of successive formation, or constituting a series of immense paral- 
lel folds ; that side of the fold in general steepest which is most remote 
from the subsiding area, (iii, 98, 1 
e. Fissures formed having the character of a series of linear rents 
either in interrupted lines or parallel ranges, instead of being single un- 
broken lines of great length, and this owing to the brittle nature and 
structure of the earth’s crust; ranges sometimes curved, either from 
or 
cause proceeding from an inequality of force along parallel lines of ten- 
sion over a subsiding area,* (iii, 185, . 
IV. Escape of heat and eruptions of melted matter from below 
through opened fissures. 
a. Igneous ejection of dikes an effect and not a cause of displace- 
ments, (iii, 99, 185. se 
b. Some points in the wider fissures continuing open as vents of erup- 
tion. The outlines of large contracting areas being liable from the 
cause just stated to deep fissurings, these therefore likely to abound 
most in volcanic vents, (iii, 98, 186.) 
c. Heat from many fissures giving origin to hot springs. 
n order not to be misunderstood, that in ac- 
i res, by the lateral 
‘i + he 
igneous action alluded to, as producin 'y app 
bh ined in large earipeaind eres which subside as a whole. The great — 
r 
unequal amount in different transv nes, connect ha : rpchaganion char- 
5 e 
acte asiest fracture, (iii, 18° :)—for these ¢ 
Jud a oh ie emtets . the subordinate curves 1 
all ik and simi : sin 
the Rant Fatice ones ie topos egros, West M indanao and the Sooloo _ to 
North Borneo, and that by East Mindanao, Sangir and North Celebes,) as well as 
the curves in the mountains of Eastern Australia, (iii, 388.) 
