THE UNITED STATES GEOLOGICAL SURVEY. 483 



feet. Special maps, for the detailed survey of areas of unusual 

 miuing or scientific interest, are made on still larger scales, up to 

 1 : 10,000. With, the increase in scale there has been an increase in 

 cost ; but the latter has been in a considerably smaller ratio than 

 the increase in the value of the maps produced. Since the begin- 

 ning of topographic surveys by the Geological Survey there has 

 been a steady improvement of methods, and the survey has been 

 making better maps during the past two years than ever before. 



Primarily the topographic maps are for the use of the geolo- 

 gist, and their scale has been determined largely by this fact. 

 "With the progress of the survey from year to year, the public 

 became more and more acquainted with the maps, and a strong 

 demand arose for the topographic maps as such. Massachusetts, 

 Rhode Island, Connecticut, and New York asked to have the 

 work pushed more rapidly within their respective boundaries ; 

 this was done on the condition that the State pay one half of the 

 cost of the work. Of the States mentioned, all have a completed 

 topographic map with the exception of New York. In the great 

 semi-arid region of the interior the maps were requested as an 

 aid in the development of their resources in artesian water and in 

 the application of drainage waters to irrigation. Severe criti- 

 cism of the survey has been made on account of the extent of 

 the topographic surveys in the semi-arid region ; but when it is 

 considered that the Geological Survey is a national institution, it 

 is evident that the great interior has as just a claim for consid- 

 eration as the mining regions of the mountain areas of the east- 

 ern and western sides of the continent. If water is the principal 

 mineral resource, it should receive due attention in making the 

 topographic map. The uses of the topographic maps are many, 

 and it is the policy of the survey to give them as high a standard 

 of accuracy as the limit of scale will permit. A map may cost 

 one dollar or one thousand dollars, or more, a square mile, accord- 

 ing to its scale and its contents. For general purposes an excel- 

 lent map can be made for ten dollars a square mile, one that will 

 subserve the uses of the geologist and the people. This will 

 answer for nine tenths or more of the area of the country ; and 

 when more detailed, expensive maps are required for the remain- 

 ing tenth, they can and will be made. In the meantime the devel- 

 opment of the country will be assisted in many ways by the maps 

 constructed on the scales now adopted. 



The following table exhibits the area of topographic work 

 completed up to December 1, 1894. Of this, a considerable por- 

 tion of the 1 : 250,000 scale (four miles to the inch) will be revised 

 as detailed geologic work is carried forward. A thorough re- 

 vision will also need to be made of certain areas in the Appala- 

 chian Mountains and west of the Mississippi River, to the Pacific. 



