EXPENSES ATTENDING MINING OPERATIONS. 
183 
zoic rocks. In the latter it ranges from the calciferous sand¬ 
stone to the Niagara; these extremes together with the included 
rocks contain veins of galena. In Europe, especially in Eng¬ 
land, it extends upwards into the carboniferous limestone. So 
far as observations have been made, this ore does not occur in 
veins in the Messozoic series. 
The foregoing facts sustain the doctrine which many distin¬ 
guished geologists have inculcated, that metalliferous veins are 
productive and important the nearer they are to the igneous 
rocks, and those districts which are rich in metals, are traversed 
and disturbed by them, The Wisconsin lead district, however, 
is much less dyked and disturbed than any other one in this 
country which is equally rich and productive in metals. 
ON THE EXPENSES ATTENDING MINING OPERATIONS. 
§ 112. It is scarcely necessary to observe that the expense of 
working a mine must depend upon a variety of circumstances, 
and that the estimate of those expenses which will probably 
accrue in the working of any given mine, will not be applica¬ 
ble to any other though the actual amount of metal may be the 
same in each. 
In some cases a work may be prosecuted successfully with¬ 
out the aid of gunpowder, in others the hardness of rock may 
become excessive at certain depths, and trap dykes may cut off 
a lode, and hence heavy expenses will be incurred, in recover¬ 
ing it. Variability in the hardness of rocks is one of the prin¬ 
cipal causes of the difference of expense in working mines 
which belong to the same rock or formation. 
Mining operations embrace three kinds of work—shafting, 
tunneling and stoping. Shafts are right-angular cuts into the 
soil and rock, in which respect they differ from wells. They 
may be perpendicular or inclined. They are necessarily per¬ 
pendicular if the lode is vertical; they may be inclined and 
sink upon an inclined lode to great advantage by employing a 
proper apparatus for elevating the mineral. But they are more 
