NATIONAL SURVEYS AND MODERN ATLASES 157 



The regular edition will be derived from the re-survey of Great 

 Britain. Contours at twenty-five feet interval will be from 

 ground survxy or from air photographs. On the provisional 

 edition, intermediate contours are interpolated. 



Since the methods of representing surface forms have been 

 closely related to printing techniques, the two may con- 

 veniently be considered together. The first edition of the One 

 Inch was printed from engraved copper plates, and relief was 

 somewhat crudely shown by hachures, very much in the style 

 of the Cassini map of France. At first, the heavy hachuring 

 tended to obscure detail, but later there was some improvement. 

 Contours were first adopted about 1830 as a result of ex- 

 perience on the Irish Six Inch survey, and were soon afterwards 

 introduced on the Six Inch and the One Inch maps of northern 

 England which completed the first edition. The contours were 

 surveyed instrumentally at 50 feet, 100 feet and thence at 

 intervals of 100 feet to 1,000 feet. Above 1,000 feet, the interval 

 was 250 feet. Considerably later, on the Popular (Fourth 

 edition) of the One Inch map, additional contours were inter- 

 polated at intervals of fifty feet. 



Since all the detail on the engraved sheets was in black, the 

 contour lines were not always conspicuous. Though hachures in 

 brown were later printed on the One Inch from a second 

 copper plate, the use of colour in general followed the introduc- 

 tion of lithographic printing or a development of it, photo- 

 zincography, in which the original was photographed and trans- 

 ferred to zinc plates for printing. In the Third edition of the 

 One Inch, completed in 1912, and known as the 'fully 

 coloured', relief was shown by hachures in brown and con- 

 tours in red. In all there were six printings, brown and red 

 for the relief, blue for water, green for woods, and burnt 

 sienna for roads, with names and other detail in black. Follow- 

 ing Bartholomew's successful production of a Quarter Inch 

 map of Britain in which relief was shown by layer colouring, 

 the Ordnance Survey employed this method on its Half Inch 

 map, produced at the beginning of this century, and also for 

 various district maps. 



In the years before 1914, experiments in the best methods 

 of showing relief were carried on vigorously. One of the most 



