Copper  Sheeting  of  Skips. 
19 
copper  slieets,  or  of  preserving  them  w'hile  in  use  against  the 
corrosive  effects  of  oxidation.  A Committee  was  ai)pointed, 
and  Davy  himself  undertook  the  experimental  part  of  the 
impiiry,  the  results  of  which  he  embodied  in  three  papers, 
read  before  the  Royal  Society  — the  first  and  second  in 
1824,  and  the  third  in  1825 — which  were  published  in  the 
Philosophical  Transactions.  Tn  June,  1824,  H.M.S.  Comet 
was,  at  the  express  request  of  the  King  of  Denmark,  ordered 
to  j)roceed  to  Heligoland  for  fixing  the  longitude  of  that  island 
in  order  to  connect  the  Danish  with  the  British  survey.  The 
Board  of  Longitude  having  recommended  that  the  voyage  should 
be  extended  as  far  as  the  Naze  of  Norway  for  the  [)urpose  of 
a.scertaining  also  the  longitude  of  that  point,  Davy  applied  to 
the  Admiraltv  for  the  use  of  the  vessel  for  the  purpose  of 
following  up  his  investigations,  and  he  obtained  the  entire 
disposal  of  the  man-of-war  after  the  original  observations  had 
been  completed. 
On  June  30,  1824,  Davy  wrote  to  his  brother  John  : “ I 
have  found  a complete  method  of  preserving  the  copper  sheeting 
of  ships  which  now  readily  corrodes.  It  is  by  rendering  it 
negatively  electrical.  My  results  are  of  the  most  beautiful 
and  unecpiivocal  kind  ; a mass  of  tin  renders  a surface  of 
copj)er  two  hundred  or  three  hundred  times  its  own  size 
sufficiently  electrical  to  have  no  action  on  sea  water.”  His 
mode  of  applying  his  theory  to  practice  was  to  affix  to  the 
copper  sheets  short  bars  of  iron  or  zinc,  properly  curved  to 
the  shape  of  the  vessels.  The  “ protectors,”  as  they  were 
called,  gradually  corroded,  whilst  the  copper  remained  un- 
attacked. The  principle  of  protection  was  perfect,  hut  its 
very  perfection  caused  an  unexpected  evil  to  arise,  for  the 
“ protectoi’s  ” allowed  of  the  adhesion  of  sea-weed  and  shells 
which  the  scaling  off  prevented.  The  failure  of  the  “ pro- 
tectors ” was  a.  source  of  grout  vexation  to  Davy.  Immediately 
after  the  publication  of  his  paper  before  the  Royal  Society, 
announcing  the  complete  success  of  his  plan,  the  Admiralty 
gave  orders  for  the  removal  of  the  “ protectors  ” on  account  of 
the  fouling  of  the  bottoms  of  the  ships. 
Dr.  Thorpe  writes  : ‘‘  Throughout  the  whole  of  this  business 
he  was  exposed  to  a number  of  vexatious  attacks,  which  greatly 
embittered  him  and  reacted  disastrously  m)on  his  health  and 
character.  So  long  as  there  was  the  ho}>e  of  success  and  the 
prospect  of  reward,  his  claim  to  the  originality  of  the  invention 
was  contested  ; no  sooner  was  the  project  abandoned  than  he 
