WILSON.] METHODS OP TOPOGRAPHICAL WORK. 305 



you will see there such numbers as (16-115), (14-115), (29-116), &c., 

 •wbicb meau simply No, 16 from Station 115, No. 14 from Station 115, 

 and No. 29 from Station 116. These numbers are obtained in the fol- 

 lowing manner: Beginning at Station 1, we sight, say, one hundred 

 j)oints.; it will be seen at once that there must be some short and effi- 

 cient method adopted by which these points can be designated when 

 sighting them from the stations that are to follow. To give each a descrip- 

 tive name becomes impossible, owing to the number and the time it would 

 take, which is a very important consideration to the topographer, for 

 his time is So much taken up by the ascent and descent of the mount- 

 ain that he is compelled to economize time in every possible manner. 

 Each point is numbered, commencing with one; these numbers are placed 

 on the sketches over or by the point to be sighted, and when the angles 

 are taken and recorded, the number of the point is placed after its angle. 

 From the next station as you sight the points, place the same number 

 after the angle, but instead of the simple numbers write (1-1), (2-1), 

 (3-1), which signify, as before stated, point 1 from Station 1, point 2 

 from Station 1, &c. j and this designation or name, as it may be called, 

 is always used thereafter, except where they are afterward occupied as 

 stations; it is then more convenient to substitute the number of the 

 station in place of the old one. 



Any new points sighted from Station 2 are numbered again, com- 

 mencing with one as before, and these become (1-2), (2-2), (3-2), and so 

 on from station to station as above, (16-115), (14-115), the first number 

 always referring to the number from the given station, while the second 

 gives the number of the station. 



This system of numbering was originally developed by myself, and I 

 have used it for several years in connection with this class of topo- 

 graphical work, and find it as short and at the same time as com- 

 I)lete a system of giving names to the many points that are neces- 

 sary to sight as any that I have seen. It also facilitates the plotting 

 very much. For instance, in plotting you come to a point in the notes 

 of Station 125 marked 14-115 ; you know at once by turning to Station 

 115 that you will find another reading on this point 14, and that you 

 will probably find it sighted from the intermediate stations. Thus much 

 time is saved in looking for the necessary checks to any point that you 

 may wish to locate. 



Sometimes the bearings are simply placed on the sketches, especially 

 of points that are not likely to be sighted often, such as minor points, 

 stream junctions, &c. ; in that case the horizontal angle is first recorded ; 

 then follows the vertical angle, with a plus or minus sign placed before 

 it to show whether it be an angle of elevation or depression, thus: 83° 

 15' + 1° 30'. 



Over the more settled portions of the country, the principal roads 

 have been meandered with compass and odometer. 



The final results of the work in Colorado will be published in the 

 form of an atlas, containing six topographical sheets drawn in contours 

 as above described. These sheets were originally drawn on a scale of 

 two miles to one inch, then reduced to a scale of four miles to one inch, 

 and engraved on stone. The projection is so constructed that the six 

 sheets may be mounted as one map. The six corresponding geological 

 sheets are printed in colors on the contour sheets as bases. 



The general drainage map was compiled mainly from the final sheets 



and is published at a scale of twelve miles to one inch. This map was 



•designed for general distribution, and gives, as well as the drainage 



system, all of the roads, trails, railroads, towns, prominent mountain- 



20 G 



