58 J. Wiiterhouso — The Applicniion of Photograplnj [No. 2, 



In the Great Trigonometrical Survey Office at Dehra Dun, during the 

 year 187G-77, 117 maps and 30 charts, besides miscellaneous diagrams were 

 photographed, and 25,529 copies printed from them ; 297 blue prints and 

 silver prints were also made. 



At the Govt. Photozincographic Office, Puna, during the same year, 

 the number of negatives taken was 2,74<5, the number of maps photozinco- 

 graphed was 1,798, and the number of copies printed off (including copies 

 of 79 lithographs) was 74,739. Since the formation of the office, in 1867, 

 to the present time 9,100 maps have been photozincographed. 



The specific advantages to be gained by the use of photography for 

 the reproduction of maps and plans are : 



1. Kapidity of production and multiplication, especially when employ- 

 ed for copying subjects containing close and intricate details. The gain 

 varies according to the amount of detail and the time that would be taken 

 by a skilled draughtsman or engraver to make the copy by hand. For 

 instance, a highly finished map that would take several months to lithograph 

 or engrave, may by the aid of photography be copied and some hundreds of 

 copies printed off within a week. 



2. The perfect fidelity with which the most delicately minute and 

 intricate details are copied. The most skilful and careful draughtsman 

 is liable to make errors in copying, and never can attain the same ac- 

 curacy of delineation, especially of minute objects, as is obtained with the 

 camera. 



3. The facility with which copies may be obtained on scales larger or 

 smaller than the original. The extent to which this may be taken advan- 

 tage of depends verj' much upon the object in view as well as upon the style 

 of the original, and the relative thickness and size of the lines and details 

 composing it ; but notwithstanding certain drawbacks and inconveniences it 

 may sometimes be attended with, this facility of enlarging or reducing the 

 scale of an original drawing with the most perfect accuracy and with the 

 absence of all personal error, is one of the most important advantages of 

 photography, and its immense superiority in this respect over the penta- 

 graph and other methods has been proved to be beyond question. 



4. The comparative cheapness of the photographic methods. The 

 relative cost of hand labour and photography is affected by several considera- 

 tions, e. g., the nature of the subject, the process employed, the number of 

 copies made and the pay of the photographers as compared with that of 

 draughtsmen. In most cases it will be found that when it is really an 

 advantage to employ photography in reproducing maps for any particular 

 purpose, the cost will^be far less than it would be by employing hand labour. 



Notwithstanding^these advantages, the use of photography as a means 

 of reproducing maps and plans for publication has not extended so much as 



