452 WISCONSIN STATE AGRICULTURAL SOCIETY. 
forces, and should be considered as two separate and distinct 
classes of phenomena. In this light let us examine them sepa¬ 
rately. 
Fissures (in connection with which mineral veins or ore de¬ 
posits are found) are always found along lines of physical dis¬ 
turbance in the earth’s crust, and are, beyond all doubt, the 
consequences of mechanical causes, or the results of mechan¬ 
ical forces acting from below. Every man who has made the 
subject of mineral veins his study will admit this to be true. 
But the character of fissures is made to depend on various 
causes, hence their diversity of form which gives diversity to 
mineral veins and ore deposits. 
In examining the causes of which fissures are the conse¬ 
quences, we have to notice not only the intensity of the ele¬ 
vating force acting beneath a given line of strata, but the re¬ 
sistance opposed to this force by the cohesive power of the 
rocks or material thus acted upon. 
If for instance the mass acted upon should be a homogene¬ 
ous mass of crystalline matter, whose cohesive power varied 
but little, and this mechanical force steadily increased till the 
tension became sufficient to overcome the cohesive power of 
the mass, a rupture would be the consequence, and fissures 
would be produced that would extend evenly through the 
entire mass. 
If on the other hand, the formation is a heterogeneous mass, 
composed of beds of rock of uneven thickness and cohesive 
force, such as alternate beds of friable sandstone and compact 
limestone, as is very often the case, the results would be very 
different If this mechanical or elevatory force should be act¬ 
ing upon these beds of rock through the medium of some fluid, 
such as heated water or elastic vapor, it would meet with but 
little resistance in the sandstone, while the compact limestone 
would oppose it with considerable cohesive force, and would 
not yield until the tension became sufficient to produce a frac¬ 
ture in the limestone, which would be, of course, along the 
line of the greatest tension. 
The effect, then, of such forces upon masses composed of 
