The  author  described  the  instrument  as  consisting  of  on  iron  stand  supporting  a
spindle.  On  the  top  of  the  spindle  revolves  a  boss,  on  which  rests  a  frame  Is  inches
in  length  by  V  ^  width.  This  frame  is  maintained  in  the  direction  of  the  wind
by  means  of  two  vanes,  facing  each  other  at  an  angle,  the  more  open  end  of  the
angle  being  directed  towards  the  spindle.  A  small  car  with  flanged  wneels  traverses
the  frame.  To  the  face  of  the  car  is  attached  a  thin  metal  plate  6  inches  squart',
and  to  the  back  a  catch  pla3ring  freely  over  some  rack-work.  This  catch  permits
the  car  to  move  towards  the"  vanes,  but  checks  its  return  to  the  spindle.  1  lie  fiico
of  the  car  is  connected  with  a  balance  contrived  on  a  somewhat  novel  principle  by
means  of  a  loaded  wheel,  and  a  lever  with  a  weight  at  its  lower  end.  j3y  means  of
this  balance  the  resistance  to  the  progress  of  the  car  increases  with  its  advance.  Tho
ratio  of  this  increase  is  expressed  in  ounces  and  pounds  engraved  on  one  side  of  the
frtmie.  A  hand  projecting  from  the  car  moves  over  the  scale  on  the  dating  index.
