16 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



under varying circumstances to furnish these records to those who may be 

 gathering statistics. 



The most trustworthy estimates of production are those that were 

 obtained for the year ending May 31, 1880, by those engaged in collecting 

 statistics of the production of the precious metals for the Tenth Census. 

 This is due to the fact that not only was the force of experts sufficient 

 to visit personally all the important mines and smelting works, but the 

 law gave them the authority to demand, if necessary, an accurate tran- 

 script of their i-ecords, and the data thus gathered were subjected to a crit- 

 ical analysis during compilation by those technically familiar with the 

 various branches of mining industry. Moreover, it was a most favorable 

 epoch in the development of the district for obtaining an accurate record, 

 since the larger mines were being systematically worked, the record of 

 their product was kept with relative accuracy, and as yet but little ore was 

 shipped out of the district for reduction and thus rendered difficult to 

 trace. 



The Census figures of production for this period are as follows : 



Leadville products daring cenaug year, 187t>-'S0. 



Gro89 weight. 



Toru. I KUos. 



I. Ore extracted | 152, 241 j 138, 1 10, 797 



n. Ore smelted ] 140, 623 127, 571, 118 



Ounea. Kiioi. 



10.603,331 329,763. 



Otmea. Kilnt. 

 1, 716 53. 36 



3,913.7 121.81 



m. Bullion prodnced by j 28,?«3| 25, 657, 921 3, 830. 2 119. 11 | 8,053,946 1 250,478 | 28, 226 ! 25, 606, 212 

 Leadville smelters. I i i I 



Ouneea. \ KUos. 

 (!) I 



9,717,819 302,224 I (?) 



In the above table, I gives the amount of ore extracted from the vari- 

 ous mines during the year and the contents of the same in silver and gold, 

 as determined by assay at the mines. 



II gives the amount of ore smelted during the year and its assay 

 value in silver and gold, including that sent out of the district for reduction, 

 as determined by the returns from smelters and sampling works. 



III gives the bullion produced during the census year by the smelt- 

 ers situated at Leadville and its contents in lead, silver, and gold. 



