MINING AND MINERAL RESOURCES. 49 
of new operators in their vicinity. The technical press is also care- 
fully scrutinized for new names. As a further means of keeping the 
directories of producers up to date, each year the lists are printed and 
distributed to producers for corrections and additions. The names 
thus obtained are placed on a tentative list and the persons or firms 
are communicated with before their names are incorporated in the 
working list. This communication is had in two ways — by a return 
postal card, and b}^ a special circular letter. 
When persons report themselves actively engaged in any mineral 
industries, their names are incorporated in the lists, and at the close of 
each year cards are sent to these producers requesting information 
concerning their products -for the calendar year. When these cards 
are returned to the Survey they are edited or corrected for tabulation. 
Where inconsistencies occur which the person in charge of the subject is 
unable to reconcile, communication is had with the producer by letter. 
This is necessary in only a small proportion of cases. Cards which 
are complete are tabulated as rapidly as possible in books especially 
prepared for that purpose, and those needing correction by operators 
are tabulated as rapidl} T as they are made complete. 
Three requests are, if necessary, mailed to producers, and the most 
important remaining unheard from after the third request are visited 
by special agents for the purpose of obtaining the desired informa- 
tion. The permanent form of the list of producers is that of a card 
index, the cards showing, in addition to the names of the operators 
and the location of the office and of the mine, the changes in the firm 
name and the total value reported for a series of years. 
As an outcome of this study of the mineral resources of the United 
States, maps showing the occurrence of iron ores, coal, building stones, 
petroleum, and other substances have been prepared and published, in 
addition to the annual volume; also special papers in regard to the 
technical conditions of various branches of the mining industry. The 
work of collecting the mining statistics for the Eleventh and Twelfth 
censuses was performed by this division of the Survey. The division 
is ready at all times to give available information to those inquiring 
into the occurrence and utilization of mineral substances, and a large 
correspondence of this nature is carried on. 
To this division are referred large numbers of mineral specimens 
for examination. It is not possible to make analyses of these speci- 
mens, but whenever such are sent in with request for analysis the 
minerals are examined as completely as may be possible without 
analysis, and the sender is advised as to whether an analysis is desir- 
able or not; if it is, a person is named by whom the analysis can be 
made at the expense of the sender. 
Where unusual demand for any mineral product has developed, 
special efforts have been made to stimulate production of adequate sup- 
Bull. 227—04 4 
