THE TOPOGRAPHICAL SURVEY OF INDIA. 255 



So soon as the country has been accurately planned, 

 the configuration of the ground has to be sketched 

 up. This process is the end and aim of all the pre- 

 ceding work. 



The first point attended to is the arterial system, 

 or water drainage, constituting the outfall of the 

 country ; whence are deduced the lines of greatest 

 depression of the ground. Next the watersheds or 

 ridges of hills are traced in, giving the highest level. 

 Lastly, the minor or subordinate features are drawn 

 in with the utmost precision attainable. ( The outlines 

 of table-land should be well defined,' says Sir A. 

 Waugh, e and ranges of hills portrayed with fidelity, 

 carefully representing the watersheds or divortia 

 aquarum, the spurs, peaks, depressions or saddles, 

 isthmuses or connecting-links of separate ranges, and 

 other ramifications. The depressed points and isth- 

 muses are particularly valuable, as being either the 

 sites of ordinary passes or points which new roads 

 should conform to.' 



And here we must draw a distinction between 

 survey and reconnaissance. It is absolutely necessary 

 in making a survey that the outlines of ground as 

 defined by ridges, water-courses, and feet of hills 

 should be rigorously fixed by actual observation and 

 careful measurement. In reconnoitring, more is trusted 

 to the eye. 



The scale of the Indian topographical survey is 

 that of one inch per mile ; the scale of half an inch 

 per mile being only resorted to in very densely 



