DESCRIPTION    OF    AUTHORITIES.  11 
UNITED    STATES    GEOLOGICAL    SURVEY   (u.   S.  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  by  barometer. 
