126 
AMERICAN GEOLOGY. 
with matter in a solid state. The filling of fissures, then, is 
supposed by many to have been effected by subterranean forces 
analogous to the forcing of fluids upwards, or in any direction, 
by the elastic force of vapors acting upon a molten mass; or a 
new way being opened, it is forced by the elasticity of vapor 
into that way. It would be difficult to disprove such a view of 
the manner, but under certain conditions it is unnecessary 
to bring to our aid the elastic force of any fluid; for a fissure 
being opened so as to communicate with a semi-fluid matter 
below, would necessarily fill instantly, in consequence of the 
vacuity of the fissure itself. It would take place in the same 
way that water rises in an exhausted receiver of an air pump; 
or it would rise up and fill the vacuity by what is sometimes 
called suction. This view comports with the remark, that 
means would have to be devised to prevent the filling of fissures 
under the present arrangement. Again, it is evident that veins 
are not always opened to the width we find them by one single 
operation of the force of tension. In the regular cooling of the 
crust, which goes on subsequent to the formation and filling of 
a fissure, it is evident that as the cooling may still go on, the 
tension or strain will begin anew. Now, under these circum¬ 
stances less force will be required to widen anew the former 
fissure; for we can scarcely suppose that the filled fissure will 
unite the torn edges of rock so as to equal at all its former 
strength of attachment: the fissure will therefore run along the 
line of the old one with ease and certainty, because that has 
now become the weak part. This will result in the addition 
of new matter to the vein; and it is not at all improbable that 
in the extent upheaved, as well as in the line of bearing, it may 
be increased. 
I am disposed to adopt the foregoing view of the manner, 
as well as that which relates to the force by which fissures are 
filled. I do not reject, however, the view which brings in the 
instrumentality of an elastic force of a gaseons fluid, by which 
the semi-fluid matter is forced upward into a fissure. Both 
