﻿504 
  Mr. 
  J. 
  E. 
  H. 
  Gordon 
  on 
  the 
  Determination 
  [June 
  17, 
  

  

  adopted 
  the 
  name 
  from 
  the 
  'Flora' 
  without 
  suspicion, 
  unless, 
  indeed 
  

   (which 
  is 
  unlikely), 
  both 
  species 
  occur 
  on 
  the 
  island. 
  For 
  the 
  satisfac- 
  

   tion 
  of 
  other 
  botanists 
  I 
  hare 
  brought 
  back 
  specimens 
  of 
  the 
  plants 
  in 
  

   spirits, 
  showing 
  flower 
  and 
  fruit, 
  as 
  well 
  as 
  dried 
  examples. 
  

  

  The 
  fern, 
  which 
  was 
  new 
  to 
  me, 
  according 
  to 
  Lady 
  Barkly, 
  may 
  be 
  a 
  

   form 
  of 
  Poly 
  podium 
  (Grammitis) 
  australe. 
  

  

  In 
  the 
  following 
  particulars 
  I 
  am 
  sorry 
  to 
  have 
  occasion 
  to 
  report 
  

   failure. 
  

  

  The 
  moss-eating 
  Lepidopterous 
  larvse 
  all 
  died 
  before 
  our 
  arrival 
  at 
  the 
  

   Cape. 
  

  

  All 
  the 
  larger 
  Algas 
  collected 
  were 
  spoilt. 
  One 
  suite 
  of 
  dried 
  ex- 
  

   amples 
  was 
  lost, 
  through 
  the 
  box 
  in 
  which 
  they 
  were 
  contained 
  being 
  

   placed 
  open, 
  in 
  the 
  ram, 
  by 
  one 
  of 
  the 
  servants 
  a 
  few 
  da} 
  r 
  s 
  before 
  we 
  

   sailed, 
  without 
  my 
  knowing 
  it 
  had 
  been 
  moved 
  from 
  its 
  place. 
  The 
  

   second 
  set, 
  gathered 
  the 
  day 
  before 
  we 
  left 
  the 
  island, 
  was 
  sent 
  on 
  board 
  

   the 
  ' 
  Supply,' 
  with 
  directions 
  that 
  the 
  box 
  should 
  be 
  placed 
  in 
  an 
  accessible 
  

   position 
  : 
  unfortunately 
  the 
  message 
  miscarried, 
  the 
  box 
  was 
  stowed 
  away 
  

   in 
  the 
  hold, 
  and 
  I 
  could 
  not 
  get 
  at 
  it 
  until 
  a 
  fortnight 
  afterwards, 
  when 
  

   almost 
  the 
  whole 
  of 
  its 
  contents 
  were 
  completely 
  decomposed. 
  

  

  Again, 
  series 
  of 
  examples 
  of 
  some 
  of 
  the 
  flowering 
  plants 
  were 
  lost 
  

   through 
  the 
  difficulty 
  of 
  attending 
  to 
  them 
  when 
  collected. 
  

  

  I 
  left 
  Kerguelen's 
  Island 
  in 
  H.M.S. 
  ' 
  Supply 
  ' 
  on 
  the 
  27th 
  February, 
  

   arrived 
  at 
  Simon's 
  Bay 
  on 
  the 
  31st 
  March, 
  and 
  at 
  Gravesend 
  on 
  the 
  

   evening 
  of 
  the 
  7th 
  May. 
  In 
  the 
  course 
  of 
  the 
  voyage 
  I 
  collected 
  a 
  few 
  

   animals 
  and 
  Algae 
  with 
  the 
  towing-net. 
  

  

  IV. 
  "On 
  the 
  Determination 
  of 
  Verdet's 
  Constant 
  in 
  Absolute 
  

   Units/'' 
  By 
  J. 
  E. 
  H. 
  Gordon, 
  B.A., 
  Gonville 
  and 
  Caius 
  

   College, 
  Cambridge"^. 
  Communicated 
  by 
  Professor 
  J. 
  Clerk 
  

   Maxwell, 
  F.R.S. 
  Received 
  May 
  5, 
  1875. 
  

  

  (Abstract.) 
  

  

  In 
  the 
  year 
  1845 
  Faraday 
  discovered 
  that 
  certain 
  media 
  possess 
  the 
  

   property 
  of 
  rotating 
  the 
  plane 
  of 
  polarization 
  of 
  light 
  passing 
  through 
  

   them 
  when 
  a 
  magnetic 
  force 
  acts 
  on 
  them. 
  About 
  the 
  year 
  1853 
  M. 
  

   Yerdet 
  found 
  that 
  with 
  the 
  same 
  magnet 
  and 
  medium 
  the 
  rotation 
  is 
  

   directly 
  proportional 
  to 
  the 
  strength 
  of 
  the 
  magnet— 
  that 
  is, 
  that 
  the 
  ratio 
  

   between 
  the 
  amount 
  of 
  rotation 
  and 
  the 
  intensity 
  of 
  the 
  magnetic 
  field 
  is 
  

   constant. 
  

  

  The 
  object 
  of 
  this 
  investigation 
  is 
  to 
  measure 
  this 
  constant 
  in 
  absolute 
  

  

  * 
  The 
  whole 
  of 
  this 
  work 
  has 
  been 
  done 
  under 
  Prof. 
  Clerk 
  Maxwell's 
  superintend- 
  

   ence. 
  He 
  suggested 
  the 
  method 
  and 
  nearly 
  all 
  the 
  details 
  ; 
  and 
  any 
  merit 
  which 
  the 
  

   investigation 
  may 
  have 
  belongs 
  to 
  him. 
  He 
  is, 
  however, 
  in 
  no 
  way 
  responsible 
  for 
  any 
  

   errors 
  there 
  may 
  be 
  in 
  the 
  numerical 
  results. 
  

  

  