146 CLASSIFICATION OF THE PUBLIC LANDS. 



the two main groups of cases in the detailed account of field methods 

 that follows, despite their clearly distinct legal status. In most of 

 the eases considered nearly all the kinds of information to be enumer- 

 ated are used to a greater or less extent, and a geologic map of some 

 kind invariably forms a part of the record. 



The metalliferous deposits examined or looked for in most of the 

 investigations preceding classification are veins, magmatic ore bodies, 

 contact-metamorphic deposits, and bodies formed by replacement. In 

 mining law these deposits are usually comprised in the term " lodes," 

 and they may conveniently be so designated here. Some cases have 

 to do with placer deposits, which are easier to examine and classify 

 than lodes. 



PSiEliUICISAKY FBOCESXTKB. 



As in the classification of nonmetalliferous lands and geologic 

 field work in general, it is the duty of the geologist, before he takes 

 the field, to gather information about the geology of the region to be 

 examined and to provide himself with a base map. Other informa- 

 tion that is especially desirable for work of this class relates to the lo- 

 cation and status of the mining claims in the region. This is the 

 only matter that requires further notice here, for the subject of base 

 maps has been discussed elsewhere and the utility of geologic in- 

 formation is self-evident. 



Plats and descriptions of patented mining claims are on file in the 

 offices of the surveyors general of the several States and in the 

 General Land Office at Washington. These show accurately the posi- 

 tion of the claims with reference to land lines or location monuments. 

 Provided with copies of these records, the examiner is able readily 

 to find the patented claims. Less complete and accurate descriptions 

 of the unpatented claims are filed in the offices of county clerks 

 with the first records of location and the affidavits on assessment 

 work. 



ITEIiD ■WOKK. 

 LOCATION AND TOPOGEAPHY. 



The methods of location used in classification of this kind may 

 be any of those described on pages 53-61. Some of the conditions of 

 classifying metalliferous land, however, influence the selection of 

 methods. The minute accuracy that characterizes much of the work 

 on coal land is not often necessary in work on metalliferous deposits, 

 and it is therefore feasible to use comparatively rough methods like 

 that of the pacing traverse, which has been employed to a consider- 

 able extent. Another influential fact is that metalliferous land is 

 more likely than nonmetalliferous land to be situated in mountainous 

 territory. This is not obvious at first glance, but as metalliferous 



