I 
APPENDIX—GEOLOGICAL SURVEY. 395 
it, I shall, as far as possible, confine myself to the following 
order: 
1. A description and classification of the phenomena of 
the lead district (that is, the observed features of the lead dis¬ 
trict as such), and their relation to the phenomena of other 
mining regions. 
2. The nature of the underlying strata, and their adapta* 
tion to mineral veins. 
3. Mineral veins in general, but those of the lead district 
in particular. 
4. Scientific, practical and theoretical considerations. 
But first of all, allow me to say that in order to get a clear 
and correct idea of the underlying rocks, and the relation of 
the mineral veins to those rocks, a vertical section was neces¬ 
sary. To obtain this there was no other way than by exam¬ 
ining the different layers of rock as they were brought to the 
surface by the gradual rise of the strata to the north of the 
lead district. In traveling, from the southern state line north¬ 
ward, one hundred miles along the fourth principal meridian 
I found a chance to examine the different beds comprising the 
lower strata of the lead district, and have laid them down in a 
map that will accompany this report. 
My object in collecting and carefully describing the phenom¬ 
ena of the lead district is to present in as clear a light as pos¬ 
sible the physical causes of which our mineral veins and ore 
deposits are the results. Unless we ignore altogether the teach¬ 
ings of nature, we must admit that mineral veins and ore-de¬ 
posits in the mineral kingdom are as much the results or fruits 
of well defined and unchangeable laws and physical conditions, 
as are the fruits and flowers in the vegetable kingdom, or ani¬ 
mals in the animal kingdom. 
But writing as a practical man for practical men, it may be 
well perhaps, to explain what I understand, and what I would 
have others understand by physical conditions, for in order to 
get a clear idea of the phenomena of mineral veins, and the 
characteristic features of mineral strata, nothing is of more im- 
f 
portance than correct knowledge of the physical conditions 
