E.— GEOGRAPHY. Ill 



in 1791 ; it is therefore, to the best of my belief, the oldest organised 

 survey in the world. The survey is a singularly complete one. A wide 

 range of maps is published, extending from the cadastral maps on the 

 1 : 2,500 scale (25 inches to the mile) to the 6-inch, 1-inch, |-inch and 

 ^-inch to the mile, as well as larger town plans and smaller scale wall 

 maps. With the exception of the 25-inch, which does not extend over 

 open moorland areas, the whole of the British Isles is completely mapped 

 on all these scales, and the sheets of every series are printed, published, 

 and on sale. But a possibly more noteworthy feature of the Ordnance 

 Survey is that all its maps from the largest to the smallest scale are the 

 result of accurate survey rigidly based on the triangulation of the 

 country. There is only one survey authority in Great Britain ; and 

 every map is based ultimately on the 25-inch map. 



The Ordnance Survey topographical maps of 1-inch to the mile and 

 smaller scales are all published in colours. On the ordinary edition of 

 the 1-inch, hills are shown by contours, but in certain special sheets 

 layer colouring and hill shading are added. On the i-inch and |-inch 

 scales layer colouring is used. The 6-inch map is printed in black with 

 red contours ; the 25-inch in black only. The characteristics of the 

 25-inch — the cadastral map of Great Britain — are that all topographical 

 features are shown ; every enclosure is numbered, and the area is given 

 in acres and decimals ; all civil division boiindaries are shown, and also 

 the positions and heights of bench-marks and spot heights. An interesting 

 feature of all Ordnance Survey maps also is that the position and nature 

 of aU antiquities are shown ; that is, of ancient ruins, earthworks, barrows, 

 tumuli, and other objects of arch<Bological interest. On the 25-inch 

 these are shown in great detail ; on other maps according to the 

 limitations of scale. There is a regular system of revision for all maps, 

 except the town plans which are not now maintained. Large scale maps 

 are revised every twenty years ; small scale every fifteen. 



The Ordnance Survey is responsible for levelling, as for all other 

 survey operations. There is a complete system of levelling throughout 

 the country, with permanently marked bench-marks. 



In England the Land Registry Office is independent of the Ordnance 



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surveys. But it has perhaps served to give a general idea of how surveys 



