276 SCIENTIFIC APPARATUS. 



1871-2 and 1872-3, another beginning of the same kind was made, 

 Maps were furnished showing the rainfall, the distribution of forests, 

 the railways, telegraphs, and lighthouses, the irrigation works, the 

 progress of surveys, and the distribution of troops (39). But 

 almost all subjects can be thus graphically treated on the basis of 

 geographical distribution ; agriculture with reference to yield and 

 area of crops, and the proportion of that yield to population ; 

 manufactures, institutions, political and ethnographic relations, 

 education, crime, religions, and medical statistics. Such work, to 

 be really satisfactory, cannot, however, precede, but must follow 

 the completion of the surveys in the field. 



The Geological Survey, which was commenced in 1851, when 

 Dr. Oldham arrived in India, but not placed on an efficient foot- 

 ing until 1856, has steadily progressed, and will eventually pro- 

 duce a complete geological map of India. The first geological 

 map, compiled from data then existing, was prepared by Mr. 

 Greenough in 1853 (40), and it is still interesting as showing the 

 state of our knowledge at that date. Since the regular commence- 

 ment of the survey many valuable maps have appeared in the 

 volumes of memoirs, but the publication of the sheets of the atlas 

 geologically coloured is dependent on the progress of the topo- 

 graphical surveys (41). Some sheets have already appeared, and 

 a few years more will see the issue of a general map of the geology 

 of India, which will hold the position which Greenough's map of 

 England, and Griffith's map of Ireland do with reference to general 

 knowledge. This map will, of course, be added to and improved 

 as the country is opened out and examined. 



It will have been seen that the supply of Maps of India flows 

 from several sources. The most important, and by far the most 

 prolific, is the office of the Surveyor-General at Calcutta. Here 

 are annually produced new sheets of the Atlas, the results of the 

 topographical and revenue surveys, and many useful compiled 

 maps. Next comes the Head-Quarters of the Superintendent of 

 the Great Trigonometrical Survey at Dehra Dun, where the great 



