NOTES. 



Topographic Survey of Canada. — Some two years ago a book on 

 the subject of photogra]3liic surveying by Mr E. Deville, sur- 

 veyor general of Canada, was issued by the Dominion land office. 

 Apparently this is a book of instructions, and treats exhaustivel}'" 

 of the methods of photographing and of using photographs for 

 constructing maps therefrom. 



Since fcAV are acquainted with this subject, it may be well to 

 characterize briefly the method of surveying b}^ photography. 

 A few points, including all occupied stations, are located by 

 angular measurements. From the occupied points, photographs 

 of the surrounding topograj^hy are taken, a complete round of 

 the horizon usually being made from each station. Devices are 

 employed for facilitating the measurement of horizontal and 

 vertical angles from the photograjjhs, and the photographs are 

 sent to the central office at Ottawa, where maps are constructed 

 from them. Angles are measured from the photographs, and 

 thus all points for location are fixed, their heights determined 

 and contour lines located. 



To topographers on the southern side of the boundary this ap- 

 pears to be a very indirect way of making a map. Most of those 

 who have studied the subject are aware that this method has 

 been experimented with by several countries and discarded by 

 all except Italy and Canada. The topographers of all other 

 countries are accustomed to making maps directly in the field, 

 using the country itself as copy, and not passing it through the 

 medium of a photograph. By this simple and direct method it 

 is believed that a iiiore lifelike transcript of the original can be 

 obtained, and, moreover, that the work can thus be done more 

 rapidly and at less expense. 



A few sheets recently issued by the Dominion land office ap- 

 pear to sustain this position. They are lithographed on a scale 

 of 1 : 40,000, relief being expressed by contours at intervals of 

 100 feet and by shading. They represent a portion of the Rocky 

 mountain region on the line of the Canadian Pacific railway. In 

 many respects these maps are very creditable i:)rocluctions. A 

 commendable attempt has been made to map a wild and un- 

 known region, and the use of hill shading, combined with con- 



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