APPENDIX—GEOLOGICAL SURVEY. 
457 
peculiar to each class of fissures. This classification would re 
suit in (what is so clearly defined iu the experience of every 
practical miner) two systems of mineral veins or mineral strata. 
In connection with these facts would come the question of rela¬ 
tive value or productiveness of the two systems, a question in 
which all connected with mining are interested. 
Now while it is evident that there is this diversity in the 
form of mineral veins, resulting from diversity in the 
forms cf fissures in which thev are found, which also results 
from a difference in the texture, cohesive and crystalline condi¬ 
tions of the strata acted upon by two or more forms of mechan¬ 
ical force, it is also evident that these forms of force are only 
modifications of one and the same force, internal heat. Upon 
no other hypothesis can we successfully unravel the compli¬ 
cated processes of mineral formations. 
I have dwelt longer upon this question of fissures than 
would be necessary under ordinary circumstances, but I wish 
to bring this question out here, because there is a tendency on 
the part of a certain class of geological observers (especially 
in this country) to regard as mineral veins only such as are 
found in fissures of undoubted plutonic origin, regarding all 
other forms of mineral or ore-deposits, as mere surface depos¬ 
its, produced by atmospheric agencies, or some other physical 
conditions acting on the surface. Such views are not only 
detrimental to all mining interests and the development of our 
mineral resources, but are in direct conflict with the phenom¬ 
ena of mineral strata generally. 
Mineral veins (I have stated before), and the fissures in which 
they are found, are two different things, formed at different 
times, under different physical conditions. Practically consid¬ 
ered, mineral veins are simply the filling up of fissures of all 
kinds with ore-deposits. The material differs widely from 
the rocks in which the fissures are found, hence we may safely 
call it foreign material. But whether this material has been 
brought into these fissures by physical causes, acting from 
above , or from below is the question that has divided the opin¬ 
ions of scientific men. 
