460 
WISCONSIN STATE AGRICULTURAL SOCIETY. 
aggregations of mineral matter, where the temperature and 
other conditions will admit of it. 
I think there can be but little doubt, if any, that the me¬ 
chanical and chemical powers of water, together with the 
forces which they generate under the influence of the varying 
degrees of heat form the essential elements in the physical 
conditions necessary to the production of mineral veins and 
ore deposits. Nor is it the action of these forces alone, but 
the beautiful system of force produced by their action and re¬ 
action upon each other that has given us the harmony and or¬ 
der that pervade mineral strata and mineral veins everywhere. 
The universal phenomena of mineral strata point to such con¬ 
ditions, and harmonize with such an origin ; nor do I know of 
a single law of nature with which it conflicts. 
Every practical miner knows well, that in the neighborhood 
of productive mineral veins, even the same formation presents 
different appearances, as though in certain places it had under¬ 
gone a change from its original condition, while in others it re¬ 
mained unaltered. This altered condition of the rock runs in 
given lines or zones, conforming fully to some directive law. 
It appears also to have been exposed to peculiar physical con¬ 
ditions subsequent to its formation, as though an unequal dis¬ 
tribution of heat or vapor, or solvents of some kind had pro¬ 
duced a marked difference in the structure, while the chemical 
composition of the mass remained the same. 
This altered rock presents more favorable conditions for fis¬ 
sures than the unaltered. . It looks almost as if it had under¬ 
gone a special preparation for this purpose. The whole mass 
seems to be traversed in all directions with fissures, filling it 
with ramifications not unlike veins in an animal, and like them 
circumscribed by natural law. They are of all sizes from a large 
dike down to a small thread-like seam, too small to be seen by 
the naked eye, but in a fine grained rock, with a magnifying 
power, they may be seen traversing it with all the regularity 
of the larger ones. And what is very strange, we have in this 
form of fissures and veins all the system and regularity, to- 
