414 A. M. BATEMAX MII.ITAEY AXD GEOLOGIC MAPPES'G 



and the readiness with which it may be constnicted will enable large 

 nnmbers to be obtained, so that each smdent may do iadividual work 

 with an individnal plane-table. For teaching students the principles of 

 location, its simplicity is an advantage rather than a disadvantage, as 

 their minds are not distracted from the subject by having to master the 

 numerous screws and adjustments of more refined iostruments. 



The equipment described here is not intended for extremely accurate 

 work, involving small allowable errors, but for such purposes as recon- 

 naissance sketch maps and geologic mapping with or without a topographic 

 map. To employ precise methods and instruments for work which does 

 not need to be precise, or from its nature is incapable of being made 

 precise, is laborious and a waste of time and money. Most geologic- 

 mapping is of this nature, for an outcrop of a bed which is irregular in 

 thickness, strike, and dip can not be located within a few inches and 

 usually not within a few feet. For such work simpler instruments and 

 approximately accurate methods are proper because of the time and ex- 

 pense saved. 



