130 A MANUAL OF TOPOGEAPHIC METHODS. 



COLORS ANIi CONVENTIONS. 



The work upon the original sheets conforms to the system of conven- 

 tions and lettering adopted by the Survey. Streams must be inked in heavy 

 Prussian blue, lettering and culture in India ink, and contours in burnt sienna. 

 Indelible inks must not be used on original sheets. Every fourth, or fifth 

 contour, whatever the contour interval, should be emphasized, in order to 

 distinguish it from the others, and the contours so distinguished should be 

 freely marked in columns with the number of feet above sea level which 

 t Ihn indicate. 



Qpon flic map should be located all towns of sufficient importance to 

 contain post-offices; all railway stations and other settlements of any impor- 

 tance ; all houses, all public roads, and, in unsettled regions, the principal 

 trails; all railroads, canals, and aceipiias; all tunnels of sufficient length to 

 be represented; bridges, ferries, fords, and dams upon streams of sufficient 

 importance to be double-lined; all glaciers, marshes, sand, and sand dunes, 

 and all state, county, and township lines. 



The convention for cities and towns must conform as closely as possible, 

 in extent, direction of streets, etc., to the actual plan of the place, and the 

 houses in the built portion should be blocked in. 



Depression contours should, if they inclose large areas, be indicated by 

 numbering them freely. If the area is small, they should be hatched, the 

 hatchings being on the side of the line toward the depression. 



The extent of forests and of flood plains will not be placed upon the 

 original maps, but should be colored upon photographs of them. 



TITLES AND LEGENDS. 



The sheets are without border or neat line, the outer projection lines 

 taking the place of the latter. Upon the margins the latitudes and longi- 

 tudes of the projection lines must be given. The titles and legends must 

 conform in arrangement and character to those on the printed sheets. 



Wherever it is practicable to do so, care must be taken to connect the con- 

 tours, streams, and culture on the margins of sheets with the adjoining sheets. 



All held work should, if possible, be platted and the work completed during 



tl See season immediately succeeding the field work, and no sheet should 



be reported as completed until it is ready in all respects to be engraved. 



