462 
CULTURE  AND  DISEASES    OF  THE  SILKWORM. 
favorably  with  that  of  a  metallic  bell  of  equal  diameter.  The 
hardest  kinds  of  wood  seem  to  produce  the  purest  and  most  har- 
monious tones.  On  account  of  its  capacity  of  conducting  heat 
and  electricity,  Sidot  recommends  the  coal  prepared  in  this  man- 
ner for  use  in  Bunsen's  galvanic  batteries,  and  for  pencils  for 
the  electric  light.  Such  pencils  give  a  much  intenser  light  than 
those  made  from  the  graphite  of  gas  retorts ;  they  become  grad- 
ually white-hot  throughout  their  whole  mass,  without  burning  at 
a  single  point,  and  cool  down  immediately  as  soon  as  the  fire  is 
removed.  Linen,  hemp,  cotton,  paper,  and  silk  behave  similarly 
to  wood,  and  the  action  of  methylated  spirits  (wood  naptha), 
hydrocarbons,  (&c.,  resembles  that  of  bisulphide  of  carbon.  The 
coal  from  wood  has  superficial  metallic  lustre,  is  denser  than 
common  charcoal,  and  has  a  greater  absorbing  power  for  gases. 
— Pltarm.  Jour.^  Lond.^  July  2,  1870,  from  Journal  of  Society 
of  Arts. 
CULTURE  AND  DISEASES  OF  THE  SILKWORM. 
Pasteur  has  recently  investigated  some  of  the  diseases  which 
attack  the  silkworm,  and  has  published  the  results  of  his  labors 
in  a  work  entitled  "  Sur  la  Maladie  des  Vers  a  Soie."  The  dis- 
ease, called  p^brine,  which  has  been  very  prevalent  and  destruc- 
tive of  late  years  in  various  parts  of  France,  has  especially  en- 
gaged his  attention 
Pebrine  derives  its  name  from  the  black  specks  Avhich  occur  on 
the  silkworm  suffering  from  it,  and  it  consists  in  the  development 
of  peculiar  parasitic  corpuscles  which  invade  the  eggs,  the  blood, 
and  all  the  tissues  of  the  silkworm.  One  of  the  observations  of 
M.  Pasteur  is,  that  the  corpuscles  are  very  easy  of  detection  in 
the  moth  of  the  silkworm,  whilst  in  the  earlier  stages  of  silk- 
worm development,  L  e.  in  the  stage  of  the  egg  and  of  the  worm, 
the  detection  of  the  pebrine  corpuscles  is  difficult  and  often  im- 
possible. 
Moths  which  are  recognised  as  sound,  produce  sound  eggs, 
whilst  unsound  moths  produce  unsound  eggs,  which,  althoogh 
themselves  showing  no  sign  of  the  disease,  cannot  develop  into 
healthy  worms. 
Pasteur's  practical  advice  to  the  silk  cultivator  was  to  examine 
the  mothy  and  to  make  sure  that  healthy  moths  were  started 
