PRELIMINARY EXAMINATIONS AND SURVEYS. 17 



stated in the report. Should no further data be necessary, the report should so state, 

 and should contain a project and an estimate of the cost of the proposed work. The 

 commencement of the improvement then only awaits the action of Congress in appro- 

 priating the funds required for carrying out the works. Should the report be unfavor- 

 able, the matter is usually dropped. If its friends are persistent, however, another 

 examination may be ordered later, but usually an adverse report is very influential 

 in defeating favorable action. 



Preliminary Survey and Report. When a preliminary survey is ordered by Act 

 of Congress its scope is usually limited by the Act itself or by the character of the im- 

 provements proposed. In general it will determine the length, width, and topography, 

 as well as the slope of the stream, it will ascertain the character of the bed and the banks, 

 and the depth of water, and will measure the discharge and velocity at various places 

 and stages. The survey may be made by the stadia, or by the ordinary methods used 

 in railroad work, but the former method will usually afford sufficient accuracy. Where 

 it is to be elaborate, parties can work advantageously on each side of the stream, con- 

 necting their work at intervals, and accompanied by a sounding party working from 

 a boat in the river, the positions of the soundings being fixed by the parties on the banks. 

 Permanent bench-marks should be established at accessible points, not more than a 

 mile apart. A survey and a line of levels on one bank, or in the bed of the river, if made 

 during low water, are usually sufficient to determine approximately the cost and the 

 number of works required, a more extensive investigation following in the vicinity of 

 the works after the general location has been established. 



The survey should be platted to a large scale and the maps should show the general 

 features of the country adjacent to the river as well as the course, depth, and width 

 of the stream itself. Sections of the river at different points, as well as a profile of the 

 river-bed, should accompany the maps. 



The report should give all the material facts determined by the survey and exami- 

 nation, or otherwise obtainable, and should especially point out the advantages which 

 might be expected to result from the improvement, the probable development of the 

 mineral resources and agriculture, the manufacturing possibilities, the quality and 

 quantity of timber, building-stone, etc. The accessibility of materials suitable for con- 

 structing the works, and their probable permanency after having been built, are also 

 matters of importance and should be noted. The population of the valley, the seasons 

 and duration of navigation in past years, the extent and period of floods and low water, 

 and the effect and character of improvements already made, if any, should also be given. 



Following these general points there should be a detailed description giving the 

 principal facts concerning each section surveyed, depth of water, character of bed, 

 obstacles to navigation, islands,, towheads, reefs, bars, etc. 



Project and Estimate of Cost. As a part of the report a project for improving 

 the river is usually required, giving the depth and width of channel to be secured, and 

 the means by which this is to be carried out. The method of improvement, as well 



