70 



dered them. His delineation of the different characters revealed 

 close study of the work : and the difficult task of giving an 

 intelligent recital of Shakespeare's " Moor of Venice "' was well 

 fulfilled. 



HOW TO READ A MAP. 



By Captain H. SPENSEE WILKINSON, M.A. 

 November 9th, 1886. 



In introducing the subject of his Lecture Captain Wilkinson 

 observed that their country was very backward in geographical 

 knowledge, and this he attributed largely to the want of good 

 maps. There was a good deal of ignorance respecting the inform- 

 ation contained in a properly constructed map, shewing the 

 requisite features. The maps used by travellers conveyed more 

 instruction than the ordinary reader imagined. The conven- 

 tional signs, that is those representing railroads, &c., should 

 first be understood. It was essential in the practice of Carto- 

 graphy that clear methods be used for representing the undula- 

 tions of the earth's surface. This was done in two ways, by the 

 effect of light and shade : and by horizontal lines which shewed 

 the difference of elevation. Under the former plan there was 

 the theory of Vertical Illumination, which assumed that flat 

 surfaces are quite white, getting as much light as possible, and 

 that absolute precipices get no light, and are therefore black. 

 The degrees of slope were therefore represented by lines which 

 gave a shade proportionate to the slope. Such maps are almost 

 without exception used for military purposes. They shew liow- 

 ever only slope of ground, the height not being ascertainable. 

 Sections can be drawn fi-om carefully prepared maps such as the 

 one-inch Ordnance Survey Map. A section of Peudle Hill was 

 sketched on the board from one of these maps. A map of the 

 Bosphorus, from surveys made by Field Marshal Moltke, in 1836 

 and 1837 was exhibited, as also a splendid example of engraving 

 of the English Ordnance Survey — the Island of Arran ; both of 

 which were on the principle of vertical illumination as shewn by 

 lines. Other maps were also referred to and a map of England, 

 one of a series for an atlas being published in France, was 

 described by Capt. Wilkinson as the most beautiful map yet 

 produced. The direction of the slope and its gradations can 

 also be shewn by tints, as exampled in a French map of Metz. 

 These maps serve only to enable a person to form a rough estimate 

 of the surface. The exact height must be given in figures, as it 

 cannot be determined from the map. The method of Oblique 



