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 should not be used for the accurate transfer of control stations and rarely for the transfer 



of shoreline, if any other type of copy can be substituted. B;;omides are always positive 



copies. 



1314. Celluloid Prints 



Contact prints can be made on low shrinkage celluloid. These have the advantage 

 of a very low shrinkage factor which is practically uniform in all directions. Such 

 prints are the most accurate copies for use in the transfer of shoreline and control sta- 

 tions. Celluloid prints are considerably more expensive than paper prints and will 

 ordinarily not be furnished unless a reason is given justifying their need. 



1315. Photographic Colors 



Most data are inked in black on the survey sheet, but various colored inks are 

 used for special purposes. In "Line Photography," which is used in chart reproduc- 

 tion, the colored inks do not reproduce equally well, and in using any photographic copy 

 of a survey this fact must be taken into consideration. In general, the colors in the blue 

 end of the spectrum are photographed with difficulty on ordinary emulsions, especially 

 when an artificial source of light is used; while those in the red end of the spectrum are 

 reproduced relatively well. Yellow photographs almost as well as black. For practical 

 purposes, it is enough to remember that the blue colors, especially blue and violet, 

 photograph poorly and may not be reproduced at all; that the red and yellow colors, 

 especially yellow, orange, and red are reproduced relatively well, sometimes as well as 

 black; and that green and brown are intermediate colors, generally but not always 

 reproducing well. The intensity of reproduction of a color seems to depend on the 

 percentage of yellow in it; for example, an orange red or a yellow green will reproduce 

 better than the purer red and green shades. The amount of pigment in any color has 

 much to do with the intensity of the reproduction. 



1316. Requests for Photographic Copies '^"^ 



Requests for photographic copies of surveys should state specifically the kind 

 desired, or the purpose for which they are to be used. In the latter case, copies prepared 

 by the most suitable method will be furnished. (See also 1314.) When photographic 

 copies of surveys are requested it will be assumed, unless otherwise stated, that they are 

 desired at the scale of the original. When they are for use in the transfer of data to 

 other sheets, they should be requested at the scale of the new survey; if an enlargement 

 is required, the reason for this must be stated. For many uses copies at reduced scales 

 will be found satisfactory if the reduction is not so great as to make the detail illegible. 

 In general, copies of surveys reduced one-half are perfectly legible. 



A request for photographic copies of surveys should specify: 



(a) The registry number of the survey, if known; or in lieu thereof, the approximate latitude and 

 longitude of the area, in addition to any field number or reference to named geographic features. 



(b) The kind of copy desired. (See also 1314.) 



(c) The scale of the desired copy. 



(d) Whether a topographic or hydrographic survey, and the approximate date thereof. 



The following examples of requests contain the required information: 



"A full-scale photostat copy of a section of the most recent hydrographic survey oil Point Judith, R. I.; photostat to be centered at 

 latitude 41°20' N., longitude 71°25' W." 



"A half-scale photographic copy of hydrographic survey by John Doe, field number Oc-4234, located in approximate latitude 

 41°20' N., longitude 71°25' W." 



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