copper. 577 



of the great Silurian escarpment which forms the bluffs extending near from 

 Magill Creek to Sponge Mountain. Some smaller isolated areas, uncovered 

 by erosion, occur in San Saba County, at the sources of Deep Creek and Deer 

 Creek. These are all in line with the Babyhead-Pecan-Cold-Field Creek belt. 

 The selected specimens reported as Nos. 79, 80, in Table I, are from Borough's 

 Prong of the East Branch of Deep Creek, where the northwestern corner of 

 the main exposed silver belt was tapped by excavations made late in 1890. 



B. BASE METALS. 



Copper, lead, and tin are the only metals of this class occurring in ores of 

 economic importance at any point in the Central Mineral Region (if we ex- 

 clude iron and manganese which fall to be treated by themselves). Zinc, as 

 explained in my former report (1889), is almost wholly absent from this dis- 

 trict, but indications of the presence of tin, possibly in proportions of some 

 importance commercially, have been detected by tests of material collected 

 by this Survey. These last results were not anticipated when that Report was 

 issued. 



1. COPPER. 



Although the outcrops of the cupriferous ores have been a little more ex- 

 plored by prospectors than in 1889, no new facts have been developed. The 

 last report by the writer contains practically all the information to date upon 

 the subject, and recent discoveries, with trifling exceptions, have been made 

 within the bounds set by that announcement. Nothing like systematic min- 

 ing has been yet attempted. Even the exploratory work has been desultory, 

 and with little or no regard to preconceived plans of operation. Whenever 

 organizations supported by adequate capital shall enter this field, with thor- 

 oughly competent engineering skill in the management, the results will be 

 such that at least one may be able to form a sound judgment as to what the 

 business chances are. The mere opening of "prospect holes" which enables 

 small specimens of rich ore to be exhibited can never afford a basis for judi- 

 cious investment, however valuable a property may actually be. It is this 

 lack of method in development more than anything else which has held back 

 the region. Those who purchase grazing lands must be content to hold or 

 sell them as such, and not as mineral lands, unless they are willing to share 

 the risks which they expect capitalists to take in proving the validity of their 

 hopes. A very good method, fair to both owner and investor, is to offset 

 capital by land to a limited extent; the investor agreeing to expend a given 

 sum in mining work, according to a stipulated plan, and receiving therefor a 

 definite interest in a small part of the property, with a fair option to acquire 

 an interest in adjoining territory, conditioned upon actual expenditure of 



