MODELS AND MAPS 141 



sentation, and to omit others, to simplify, and to conventionalise. 

 That is to say, the work must not be done by a mechanical 

 process, but by hand, after a careful determination of the 

 principles guiding selection. Indeed, as a matter of fact, it is 

 found necessary to issue four styles of these maps, each adapted 

 for special purposes. One is in plain black, and shows prominently 

 only the human topography and streams, the relief being indic- 

 ated by inconspicuous contouring. A second type is the same 

 map, but in place of contouring the relief is shown by hill- 

 shading (Fig. 39). The third form has the human topography in 

 black, and the relief in brown, thus avoiding a certain amount 

 of confusion in the lines. But the best form of all is now issued 

 in colour. In this the roads, towns, houses, and other parts of 

 the " human topography " alone are in black, water is in blue, 

 contouring in red, and a light hill-shading in brown. In addition 

 to this first and second class roads are shown in ochre, and woods 

 in green, two unfortunate additions which have deprived the map, 

 otherwise one of the best maps issued anywhere in the world, 

 of some of its usefulness to students of geography. 



In maps on this scale the size and relative position of places 

 are accurately shown, but there is no attempt to retain the exact 

 size and shape of smaller objects, though their position is kept 

 correct. Thus the breadth of roads is much exaggerated, and 

 there is no attempt to render their minor features ; but their 

 exact directions are rigidly expressed, and they are divided into 

 three classes according to their breadth, the classes being shown 

 by different types of lines, so that they are easily read. Correspond- 

 ing conventions are used for railways, canals, streams, footpaths, 

 etc., and the greatest care is taken to insert as much information 

 as possible in the map consistently with retaining clearness and 

 legibility. The study of part of a large town with a magnifying 

 glass will show the extraordinary care which has been taken 

 to secure minute accuracy in detail. 



It should be mentioned here that the Ordnance Survey is 

 prepared to supply maps of the various scales to schools and 

 other educational institutions in quantity at exceedingly cheap 

 rates, so that nothing now stands in the way of the liberal use 

 of them for educational purposes. 



