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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