endlich.] SAN JUAN MINES. 237 



It may be of interest to mention that near Lime Creek, some distance 

 down the Animas, proceeding from Baker's Park, prospecting has 

 been done for chloride-ores, in the Devonian limestones of that region, 

 although without any decided success. Almost all the mountains in 

 the immediate vicinity of Baker's Park, and the regions north of it, 

 contain veins ; frequently, however, without the remunerative metals. 

 They have been found of almost incredible width, and extending, well 

 defined, for miles. In a country where so large an amount of mineral 

 substance is present as in that which formed the field of our labors dur- 

 ing the summer of 1874, it cannot be astonishing that veins or even ores 

 should be found at any place where the conditions for their segrega- 

 tion and accumulation were in the least favorable. 



Owing to the rugged character of the country, to the sharply-cut 

 walls, inclosing canons of considerable depth, and lastly to the regularity 

 of the veins in course and dip, mining can be carried on at compara- 

 tively slight expense should the veins eventually prove as remunera- 

 tive as their surface indications might justify us in presuming. A well- 

 regulated system of sinking shafts and driving tunnels, either to or on 

 the same vein, would afford facility for the regulation of water and air,- 

 as well as for the first transportation of ore, that ought not to be over- 

 looked. Frequently the same vein can be taken in work from above 

 in a vertical direction, while 1,000 feet below a tunnel driven will 

 afford the facilities above indicated, besides furnishing valuable infor- 

 mation as to the constancy of the ore, both in character and distribu- 

 tion. Timber exists in sufficient quantities to last for many mines. 

 One unfavorable circumstance is the short duration of the season dur-„ 

 ing which active work near the surface can be accomplished. After the 

 mines have reached a certain development, however, so that their interior 

 will be but little affected by the outside influence of atmospheric changes, 

 a great portion of this trouble* will be obviated. 



In summing up all that has been observed during the short time that 

 could be allowed for investigation of this interesting mining-region, it 

 becomes necessary not to overlook the difficulties that had to be over- 

 come. Above all, the fact that all the mines were but in their infancy 

 will tend to cast a shadow over the conclusions that may have been 

 drawn with reference to many important features. In consequence of 

 this fact, no reliable data with reference to the vertical distribution of 

 the ore can be given, and, although outcrops along numerous points of 

 any lode may everywhere show favorable indications, nothing but a 

 future development of the new mines can disperse all doubt. Eegard- 

 ing the persistency of the veins in a vertical direction, a sufficient num- 

 ber of observations have been made to lead to the conclusion that their 

 general character in that respect is satisfactory. The ores contained in 

 the veins are of such composition that they will offer no serious obstacles 

 in any smelting establishment that may be founded upon principles that 

 are not totally at variance with chemical and physical laws. 



Geologically, the veins of our district are very young, probably having 

 been formed at the close of the Cretaceous or the beginning of the Ter- 

 tiary period. The enormous eruptions of the trachytic lava, covering a 

 continuous area of more than five thousand square miles, must have 

 taken place at the geological period above indicated. In the beginning 

 of this paper particular stress was laid upon the impregnation with 

 mineral matter of certain volcanic strata — a phenomenon that occurs 

 over a large tract of country. This shows that at the time of the 

 eruptions such conditions existed as were favorable to the formation of 

 that class of minerals generally termed ores. It is furthermore to be 



