VARIETIES. 
379 
semblance  to  the  Chinese  green  Lo-kao.  It  is  prepared  in  the  following 
way:- — The  bark  of  the  buckthorn  is  put  into  boiling  water  and  after  boil- 
ing some  minutes,  the  contents  of  the  vessel,  bark  and  water  together,  are 
turned  into  an  earthen  pan,  and  covered  up  that  they  may  cool  slowly. 
After  some  days  the  liquid,  which  is  of  a  brownish  yellow  color,  is  poured 
off,  and  clear  lime  water  is  added  to  it.  It  is  then  exposed  in  shallow 
dishes  to  air  and  light  under  the  influence  of  which  the  color  soon  changes 
to  green,  and  a  deposit  of  the  same  tint  settles  in  the  dishes.  Carbonate 
of  potash  is  afterwards  added,  which  produces  a  green  precipitate,  the  fluid 
taking  a  dark  brown  color.  When  the  precipitate  has  deposited,  the  fluid 
is  poured  off,  and  the  precipitate  collected  on  a  filter  and  dried.  Glenard 
in  a  report  addressed  to  the  Lyons  Chamber  of  Commerce  {^Bulletin  de  la 
SocUte  cV Encourage.  November,  1860),  has  recommended  the  discoverer 
of  this  dye  for  the  prize  of  6000  francs  offered  by  the  chamber  in  1857,  for 
a  color  like  the  Chinese  green  extracted  from  a  home  plant. — Chem.  Neivs, 
London,  June,  1861. 
Capture  of  Whales  hy  Means  of  Prussic  Acid. — A  very  interesting  paper 
has  just  been  published  by  Professor  Christison,  the  result  of  some  experi- 
ments suggested  as  long  ago  as  1831  by  Messrs.  W.  and  G.  Young,  of 
Leith,  for  the  capture  of  whales  by  means  of  poison,  the  agent  being  hy- 
drocyanic, or  prussic  acid.  This  poison  was  contained  in  glass  tubes,  in 
quantity  about  two  ounces.  Among  other  difficulties,  one  was  to  discharge 
the  poison  from  the  glass  tubes  at  the  right  time.  After  various  trials,  the 
plan  fixed  upon  was  to  attach  firmly  to  each  side  of  the  harpoon,  near  the 
blade,  one  end  of  a  strong  copper  wire,  the  other  end  of  which  passed  ob- 
obliquely  over  the  tube,  thereby  securing  it  in  its  place,  then  through  an 
oblique  hole  in  the  shaft,  close  to  the  upper  end  of  the  tube,  and,  finally, 
to  a  bight  in  the  rope,  where  it  was  firmly  secured.  By  these  means  the 
rope  could  not  be  drawn  tight,  as  it  would  when  the  harpoon  attached  to 
it  struck  the  whale,  without  crushing  the  tubes  ;  the  poison  would  then 
enter  the  whale,  and  death  ensue.  The  Messrs.  Young  accordingly  sent  a 
quantity  of  tubes  charged  with  the  poison  by  one  of  their  ships  engaged 
in  the  Greenland  fishery,  and  on  meeting  with  a  fine  whale  the  harpoon 
was  skilfully  and  deeply  buried  in  its  body ;  the  whale  immediately 
"  sounded,''  or  dived  perpendicularly  downwards,  but  in  a  very  short  time 
the  rope  relaxed,  and  the  whale  rose  to  the  surface  quite  dead  ;  but  the 
men  were  so  appalled  by  the  terrific  eSect  of  the  poisoned  harpoon,  that 
they  declined  to  use  any  more  of  them.  Subsequent  experiments  tend  to 
convince  the  learned  professor  that  success  will  be  established  in  this 
method  of  capturing  whales. — London  Pharm.  Journ  Aug.  1860. 
On  the  Density  of  Ice. — Considerable  discrepancy  exists  between  the 
numbers  assigned  by  different  experimenters  as  representing  the  sp.  gr.  of 
