A DICTIONARY OF -ALTITUDES IN THE UNITED STATES. 



(Fourth edition.) 



By HENRY GANNETT. 



INTRODUCTORY NOTE. 



This edition is greatly enlarged over earlier ones, mainly by the 

 addition of altitudes determined by railroads and of bench marks 

 of this and other Government organizations. Owing to the fact 

 that many railroads have changed their alignments and grades in 

 recent years, thus changing the heights of their stations, a general 

 attempt was made to obtain new profiles for use in this edition, and 

 the attempt has been in great part successful. This course has made 

 necessary a readjustment of the profiles and has caused many 

 changes of greater or less magnitude in the heights of stations. 



DESCRIPTION OF AUTHORITIES. 



The following is a descriptive list of the authorities from which the 

 altitudes used in the dictionary have been derived, together with a 

 brief account of the methods employed and such notes as will 

 enable one at all conversant with the methods of determination of 

 heights to form some idea of the accuracy to be expected from the 

 figures given. 



ADIRONDACK SURVEY. 



The determinations credited to this survey are from the Trig- 

 onometric and State Land Survey of New York, under Mr. Verplanck 

 Colvin. Most of the determinations were made by barometer. 

 Some, however, were determined by trigonometric methods and by 

 level. They are all located within the Adirondack region. 



APPALACHIAN CLUB. 



Most of the determinations credited to this source have been com- 

 piled from "Appalachia." They are barometric determinations, or 

 at least depend upon barometric bases. 



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