1832 REPORT OF THE CHIEF OF ENGINEERS. 



Of the localities passed through, Silverton and Lake are the best developed and un- 

 doubtedly the richest mineral-bearing regions, including in the latter the Uncom- 

 pahgre. The mountains about Silverton, Cunningliam Gulch, &c, are more massive 

 than at Lake ; tremendous, precipitous crags, which, from appearance would yield 

 more than Lake under the same impulse of capital. 



In the country as a whole there are no placers ; placers are but will-o'-the-wisps, 

 and upou the deep-seated lodes alone must reliance be placed. 



Silver is the standard product of the mines, and is found in general in fissure veins 

 well defined with surface outcroppings, commonly called the "blossom rock," which 

 was noted as frequently of chlorine and carboniferous formation. They can be often- 

 times traced with the naked eye, readily with a glass, over the mountain-side for 

 miles. The geological structures are in primary and secondary states ; the precious 

 metal is sometimes found native, as in the rich specimens of the Galma district, but 

 ordinarily as ore, in various states and mineralogical conditions, being combined with 

 pyrites of copper, noticeably about the Dolores, pyrites of iron, galena, chlorine, anti- 

 nionial lead and zinc blende or its sulphuret; rich, free ores occur, azurite or blue car- 

 bonate of copper, tetrahedrite or gray copper, sulphurets or silver glance, including 

 both sternbergite of iron and stromeyerite, of copper constituency, discrasite or anti- 

 monial silver and stephanite or brittle sulphuret of silver. 



The quartz and gangue are sometimes rich in mineral (commonly known as the 

 "vein" by prospectors and others), while the true veins or streaks (ordinarily spoken 

 of as "pay-streaks") often, and in general do, carry more; occasionally native, spec- 

 ular or dross silver, being dentiform, capillary, and disseminated, but seldom massive, 

 the luster being glimmering, fracture hackey and fine ; with galena the diminution of 

 cleavage-planes and the approach to lustrous, sparkling particles is hailed with de- 

 light by prospectors as indicating a higher proportion of argentiferous mineral. The 

 narrow rich veins, or pay-streaks, to adhere to the popular usage of the word, yield so 

 small a quantity that for a highly profitable mine dependence must often be, and in 

 general is, placed upon large amounts of well paying gangue. The oldest and richest 

 mines of the country, as in Nevada, &c, are low grade but in immense quantities. 



Although the fissures of the Uncompahgre, &c, have been pronounced to be of but 

 comparatively shallow depth by a distinguished mining geologist, not extending 

 below the great bands of breccia that may be often at a distance seen encircling a 

 mountain, increased depth has, in all cases, been well repaid. As yet, however, deep 

 mining is almost a novelty in Colorado, and in the San Juan development has not 

 advanced beyond the primary stage ; the only deep and largely developed lodes are at 

 Georgetown (silver) and Central City (gold), in both localities expenditure therefor 

 being well rewarded. 



CHAPTER VI.— BOTANY. 



Prefatory. 



A botanical collection, as well as all work relating to natural history, being wholly 

 subordinate to the main objects of the reconnaissance, could necessarily be little more 

 than of a meager character. 



Even if a collector should possess the requisite knowledge of this extensive branch 

 of natural science, the study of a •lifetime, and the thorough proficiency in collecting 

 which is only acquired through long and arduous devotion to the theory and practice 

 combined, ample time must be at his disposal to enable him to prosecute his labors in 

 the field with but a single end in view. 



The absence of all 'these essential conditions will therefore be remembered in the 

 examination of the results attained, and that the time given thereto was that usually 

 devoted by others to rest and recreation after the day's march, and in general near or 

 after dark, the specimens being ordinarily gathered on the way. 



Not with the expectation of finding any new forms, but simply to aid botanical in- 

 vestigators in denning range-limits of certain flora, was the collection made. 



For its classification, gratis, we desire to express our sincere gratitude to Professor 

 Gray, the distinguished botanist. 



Aware of the heavy demands upon his time in many ways, the vast amount of gen- 

 eral botanical research upon which he is engaged, and which no other American can 

 accomplish, and particularly on account of the knowledge of his having in charge, in 

 conjunction with his eminent English co-laborer, Sir Joseph Hooker, extensive explora- 

 tions and reports upon the Rocky Mountain flora for one of the surveys of the national 

 government, the request for such labor was not made without misgiving. 



For his promptness and kindness, and the devotion of time and unrewarded atten- 

 tion to the collection, we desire to express our grateful thanks. The classification will 

 be found hereafter as Section I. 



Mr. T. S. Brandegee, civil engineer, of Canon City, Colo., a well-known investigator, 

 and the only botanist, as we were informed by Professor Gray, who is practically 



