bmmons.;] INVESTIGATION OF METALLIFEROUS ORES. 27 
logical structure and relations of the vein. So many new facts were 
thus learned, and so important was their bearing upon the theory of 
vein formation, that it was judged wise to make a second and more 
exhaustive study of the copper veins of the region. This has been 
carried on by Mr. Weed and his assistant since the spring of 1901 
almost continuously, though his work has been interrupted at times 
by the necessity of completing other pieces of work. It was not 
thought best to hurry this work to completion, for the reason that the 
geological questions at issue had most important bearing in the liti- 
gation that was going on, and it was desired to avoid, as far as possi- 
ble, influencing the results of this litigation, lest there might be a feel- 
ing that the opinions expressed, which must necessarily favor one 
side more than the other, indicated a partiality to the favored side. 
The work is now approaching completion, but, on account of its mag- 
nitude, will not be published for some time. A brief summary of the 
important results is given by Mr. Weed on later pages. 
NEVADA. 
A new mining district in southern Nevada has sprung into sudden 
prominence bj T its shipment of rich gold ores to the smelters, espe- 
cialty at Salt Lake. Nevada has hitherto been regarded as essen- 
tially a silver-producing State, and mining there has languished since 
the fall in the price of the white metal, hence the development of its gold 
resources is of the greatest importance. A brief account by the writer 
of the important gold mine at De Lamar, in southeastern Nevada, was 
published in the Transactions of the American Institute of Mining 
Engineers in 1901. 
During the autumn of 1902, J. E. Spurr, after assisting Mr. Spencer 
in the Grand Encampment work during October, was detailed to 
examine this new (Tonopah) district of Nevada. lie had been taken 
ill with typhoid fever just at the opening of the field season in July, 
hence was obliged to commence his field work at so late a date that 
he found it advisable during the winter to make microscopical and 
chemical studies of his rock specimens at Washington. He will com- 
plete his field work in the spring and early summer, and a reconnais- 
sance will then be made of neighboring mining districts in the Silver 
Peak quadrangle and elsewhere. 
SOUTH DAKOTA. 
Economic Resources of the Northern Black Hills, by J. D. Irving and S. F. 
Emmons. 
This work was designed to be published in conjunction with the 
Sturgis-Spearfish folio, for which the field work was completed some 
years since. Its publication has been delayed by the calling off of the 
principal author, T. A. Jaggar, jr., to other duties, notably to the study 
