APPENDIX—GEOLOGICAL SURVEY. 
473 
I have stated before, and will repeat it here, that the phe¬ 
nomena of the lead district and of the formation north of it 
along the same axis, not only fully harmonize with the theory 
of the hydro-plutonic origin of our fissures and ore deposits, 
but readily explain them. By hydro-plutonic origin I mean, 
as explained before, the force of internal heat acting through 
water as a medium ; a form that is related or rather correlated 
to plutonic force, as heat and motion, or electricity and magnet¬ 
ism are related to each other; or as Professor Tyndall would 
doubtless call it, a different mode of motion. 
Unless we reject altogether the teachings of natural law, and 
regard our ore deposits as the result of chance, our choice of 
theory must be between this (or a similar one) and one that 
teaches their surface origin by atmospheric agencies. Before 
we adopt the latter, let us reflect for a moment upon what we 
shall be called upon to explain by it. It will not be the pheno¬ 
mena of our ore deposits merely, but also the fissures in connec¬ 
tion with which they are found; the directive forces by w,hich 
they were brought into belts of definite bearing ; the axis of 
elevation to which these mineral belts, mineral fissures and 
ore-deposits belong ; for they are all related by indissoluble 
bonds that we cannot sever. And should we succeed in ex¬ 
plaining these phenomena in this way, we must also explain by 
the same theory, mountain ranges, lines ot volcanic action, 
earthquakes, and indeed all the phenomena we call volcanic, 
plutonic, metamorphic and hydro-plutonic, for all these phe¬ 
nomena are the result of the different forms, or modified forms, 
of the same force , and that force we know to be heat. 
This whole matter then, resolves itself into this: Is the 
source of this heat found in the centre of the solar system, or 
in the centre of the earth? We leave this question to the 
common sense of the people. 
Although I regard the evidences furnished in the phe' 
nomena of the lead district ample to establish the relation of 
our mineral veins to physical forces and conditions acting 
from below; and believe that the results in other ore-districts 
similar to this favor the probability of their being productive 
