DESCRIPTION OF AUTHORITIES. 11 



UNITED STATES GEOLOGICAL SURVEY (u. 8. G. S.). 



A vast number of elevations are credited to this source. They 

 have been determined by various means, but almost entirely by 

 trigonometric methods and by level lines. Elevations of mountains, 

 hills, and other points used as triangulation stations have, as a rule, 

 been determined by trigonometric methods. Elevations of towns, 

 railway stations, and the like have commonly been determined by 

 spirit leveling, most of which is of sufficient accuracy to be classed as 

 precise. Since the year 1895 the leveling operations of this organi- 

 zation have been extensive, and the altitudes of great numbers of 

 points have been determined. This leveling has been carried on 

 wherever surveying for the preparation of maps has been in progress, 

 and is therefore scattered widely over the country. 



UNITED STATES LAKE SURVEY (U. S. L. S.). 



Under this heading are given altitudes determined by the United 

 States Lake Survey. They include the altitudes of stations in the 

 triangulation, determined by trigonometric methods, and the 

 results of a line of precise levels from Albany through the Great 

 Lakes. 



WATER POWER OF MAINE. 



These elevations were extracted from a State report bearing the 

 above title. 



WEATHER BUREAU. 



The elevations credited to this authority are those of its stations, 

 meaning thereby the cistern of the barometer, in case that instrument 

 is in use. Included here are not only the regular stations, but those 

 of the volunteer observers. 



These elevations have been determined by the best means avail- 

 able; that is, by connection with lines of precise levels, with rail- 

 road levels where practicable, or, in default of these, by barometric 

 observations. 



WHEELER, CAPT. GEORGE M. 



To this authority are credited all elevations determined by the 

 United States Geographical Surveys West of the One Hundredth 

 Meridian. Nearly all the work is either barometric or trigonometric 

 depending upon barometric bases. 



WHITNEY, PROF. J. D. 



Under this authority are given elevations determined by the Geo- 

 logical Survey of the State of California. All determinations are 

 barometric. 



WILLIAMSON, LIEUT. R. S. 



These elevations were determined bv barometer. 



