and  Registering  the  Force  and  Direction  of  the  Wind.       33 
The  best  direction-instrument  at  present  in  use  is  that  in- 
vented by  Messrs.  Beckley  and  Casella,  in  which  a  moving  chain 
is  substituted  for  the  shaft.  In  this,  however,  there  must,  I 
think,  be  some  momentum,  and  the  chains  must  pass  in  an 
approximately  straight  line  from  the  vane  to  the  printing- 
instrument. 
>  In  the  electrical  anemometer  there  is  no  momentum  whatever. 
The  (four)  wires  being  stationary,  can  pass  anywhere  where 
most  convenient ;  for  instance  they  can  come  down  outside  the 
house  and  enter  through  a  gimlet  hole  in  the  window-frame. 
The  cups  and  fans  can  be  placed  at  any  distance  from  the 
printing-instrument.  For  instance,  the  vane  might  be  at  Ports- 
mouth and  the  printing-instrument  in  the  meteorological  office 
in  Westminster*.  Very  small  battery-power  is  required;  six 
Walker  cells  are  used,  with  acid  diluted  14  to  1,  equal  to  rather 
less  than  one  Grove's  cell. 
The  direction-apparatus  is  moved  by  a  set  of  Beckley  fans, 
the  force  by  a  set  of  Robinson's  cups. 
The  mechanism  is  as  follows  : — 
The  Direction  Contact-apparatus. 
On  the  axis  (Plate  I.  fig.  1)  of  the  fans  is  a  crown  cog-wheel 
with  256  teeth,  which  gear  into  a  wheel  of  16  teeth,  giving  a  mul- 
256 
tiplying-power  of  ^-^-  =16,  thus  causing  a  horizontal  axis  to  re- 
volve once  every  time  the  hand  moves  a  point — that  is,  counting 
girouette,  et  placee  a  l'air  libre,  est  an  rose  de  quatre  secteurs  metalliques 
garnis  de  platine,  contre  laquelle  vieut  s'appuyer  une  languette  fixee  sur 
l'arbre  de  la  girouette. 
"  L'appareil  est  muni  de  quatre  telegraphes  dont  les  electros  sont  respec- 
tivement  en  communication  avec  les  quatre  secteurs;  ehacun  des  quatre 
telegraphes,  en  faisant  osciller  son  levier  selon  la  direction  dans  laquelle  la 
girouette  ferme  le  circuit,  donne  Fun  des  quatre  vents  principaux.  Les 
vents  intermediaires  aux  quatre  principaux  s'obtiennent  par  la  combinaison 
des  deux  voisins.  Cette  combinaison  se  produit  soit  par  l'oscillation  de  la 
girouette,  soit  par  l'indication  simultanee  dc  deux  telegraphes. 
u  L'experience  a  prouve  que  dans  la  pratique  ce  systeme  satisfait  aux 
besoms  dela  science  meteorologiquc  actuelle." — Etudes  Religieuses,  Histo- 
riques  et  Litteraires,  par  les  Peres  de  la  Compagnie  de  Jesus. 
In  this  it  will  be  seen  that  five  wires  (four  line  and,  of  course,  a  return) 
are  employed  to  give  8  points  of  the  compass.  My  instrument  gives  16* 
or  32  points  with  three  wires.  The  paper  on  which  the  wind  is  recorded 
in  Padre  Secchi's  instrument  has  to  be  changed  every  ten  days.  The  in- 
strument also,  as  far  as  I  understand,  works  with  a  closed  circuit.  The 
contact-breaker,  however,  is  no  doubt  simpler  than  mine,  and  has  the  ad- 
vantage of  using  a  vane  instead  of  Beckley  fans. — J.  E.  II.  G.,  December 
16,  1871. 
*  In  the  instrument  lately  erected  at  Eton  the  fans  and  cups  are  45 
yards  from  the  registering  instrument. 
Phil.  Mag.  S.  4.  Vol,  43.  No.  283.  Jan.  1872.  D 
