10  DICTIONARY    OF    ALTITUDES    IN    UNITED    STATES. 
the  results  of  which  can  be  absolutely  depended  upon  for  accuracy. 
The  United  States  Coast  and  Geodetic  Survey  has  executed  a  vast 
amount  of  leveling  of  the  greatest  accuracy,  including  a  line  across 
the  country  from  Sandy  Hook  through  St.  Louis,  Denver,  and  Ogden 
to  Puget  Sound. 
The  United*  States  Lake  Survey  and  the  Mississippi  River  and 
Missouri  River  commissions  have  also  made  important  contributions 
by  leveling  numerous  lines  in  the  Mississippi  Valley  and  about  the 
Great  Lakes. 
The  United  States  Geological  Survey  has,  in  connection  with  its 
topographic  work,  carried  on  extensive  leveling  operations  scattered 
over  many  different  localities  in  various  parts  of  the  country.  This 
work,  done  since  the  year  1895,  has  already  reached  such  magnitude 
as  to  form  a  very  important  aid  in  the  adjustment  of  levels. 
Moreover,  as  above  noted,  the  railroads  have  aided  greatly  in  this 
work  of  adjustment  by  carefully  compiling  the  levels  of  their  own 
systems,  and  the  elevations  given  by  many  of  the  larger  railroad 
companies  of  the  country  are  nearly  or  quite  as  accurate  as  the  pre- 
cise levels  above  specified  and  can  safely  be  used  as  primary  lines. 
RAYNOLDS,   CAPT.  W.  F. 
Under  this  autnority  are  given  the  hypsometric  results  of  the  expe- 
dition of  Captain  Raynolds  to  the  country  about  the  sources  of  the 
Snake  and  Missouri  rivers  in  1860-61.     All  the  work  is  barometric. 
SIMPSON,  CAPT.  J.  H. 
Reconnaissance  in  Navajo  Country,  1849  (Thirty-first  Congress, 
first  session,  Senate  Document  No.  6),  and  Explorations  in  the  Great 
Basin  of  Utah,  1859,  published  in  1876.  The  elevations  were  meas- 
ured by  barometer. 
UNITED   STATES   ARMY    (u.    S.   A.). 
Under  this  heading  are  given  the  altitudes  of  certain  army  posts, 
determined  by  barometer. 
UNITED    STATES    COAST    AND    GEODETIC    SURVEY  (U.  S.  C.  &  G.  S.). 
The  elevations  credited  to  this  source  are  of  two  classes — one  of 
triangulation  stations  whose  heights  have  been  determined  by  refined 
trigonometric  methods,  the  other  of  lines  of  precise  leveling  referred  to 
above. 
UNITED    STATES    ENGINEER    CORPS    (ENGINEER  CORPS) . 
Elevations  given  under  this  authority  are  the  results  of  precise 
leveling,  executed  in  connection  with  river  and  harbor  improvements. 
