288 CARNEGIE INSTITUTION OF WASHINGTON. 



tricts SO remote or so difficult of access that the Chinese can not 

 utilize the timber, and slopes which are not in cultivation become 

 overgrown with shrubs. 



These observations of destructive and constructive activity in dif- 

 ferent stages of progress afford important suggestions for the people 

 of less densely populated countries. The photographs secured 

 strikingly illustrate the facts noted. 



CONTRIBUTIONS TO GEOGRAPHY. 



Mother-maps of China. — The original surveys upon which maps of 

 China are based are of four classes : Chinese maps ; the astronomical 

 positions determined by the Jesuits prior to 1730; travelers' route 

 traverses ; and modern surveys by military intelligence branches of 

 the English, German, French, and Russian governments. Trav- 

 elers' traverses, 'executed with compass, barometer, and rude methods 

 of measuring distances, have supplied the greater part of cartographic 

 data ; and the contribution of Baron von Richthofen is conspicuous 

 in all maps of districts through which he journeyed. The recent 

 surveys b}' military officers in north China have not been extended 

 beyond the great plain, except perhaps along certain principal high- 

 ways, and in Shantung, where the Germans are making a detailed 

 map. The geographic surveys of the Carnegie expedition are con- 

 tributions which, for accuracy of positions, rank with the best of 

 the military surveys, and in topographic expression excel them. 



Methods of Topographic Survey. — In general the methods of the 

 survey were those developed with the plane-table in the western 

 United States by the United States Geological Survey, except that 

 primary triangulation points were not available. When practicable 

 a base line was measured, triangulation was expanded from it by 

 theodolite or plane-table, and stations were occupied with the plane- 

 table for location of numerous points by intersection and for topo- 

 graphic sketching. Where this graphic triangulation was not prac- 

 ticable a stadia traverse was carefully run. Relative altitudes were 

 determined by vertical angles. At Paoting fu the elevation of the 

 Belgian railway was taken as a datum, and heights above sea-level 

 were thus closely determined. Elsewhere a datum based on aneroid 

 barometers was the best available, and absolute elevations are merely 

 approximate, although relative heights are as nearly correctly deter- 

 mined as the vertical-angle method permits. 



Throughout Mr. Sargent's work determinations of latitude were 

 made both by sextant and by observations on Polaris whenever con- 



