APPENDIX—G EOLOGICAL SURVEY. 
459 
many years, and in almost every class of rock and form of 
fissure, but have not yet seen a vein, the formation of which 
could be explained by plutonic or igneous action. Fissures 
may be, and no doubt are in many cases, the result of such 
conditions, but the filling of these fissures with mineral mat¬ 
ter, I think never is. 
The nature of this material, and its arrangement in the 
fissure show beyond doubt that it is the work of chemical 
forces, and that too, of chemical forces acting through water 
as a medium. Perhaps, it would be stating the fact in a 
simpler form, and be equally near the truth to say that mineral 
veins are the results of the mechanical and chemical powers of 
water under the influence of heat. 
We are all familiar with the fact that water, when heated 
up to a certain point and under great pressure, generates a 
mechanical force of almost unlimited powers. Let me here 
notice another fact with which we are also familiar; that water, 
when heated, becomes a strong solvent, and stimulates chemi¬ 
cal activity to a high degree. Aided by other solvents which 
it holds in solution, there is hardly any solid but will yield 
to it’s power. At a high temperature under great pressure, it 
is capable of dissolving and holding in solution a vast amount 
of material, whether that material is brought under its influ¬ 
ence in the shape of solid rock, or gaseouf emanations. In this 
heated water, saturated with mineral matter, we find also an¬ 
other class of chemical forces, ready at the lowering of the 
temperature to aid, by their natural affinities and reactions, the 
work of molding this material into solid and symmetrical 
forms, such as we find in the filling of mineral fissures. And 
again, the point of temperature at which water is converted 
into steam (and consequently into mechanical force) is the 
point, or about the point, at which gases and fluids meet. At 
this point gaseous emanations and metallic sublimations rising 
through fissures from the heated interior must necessarily be 
condensed in water and driven up by mechanical force through 
fissures in the rocks above, to be deposited along their sides as 
