564 
VARIETIES. 
manufactures  as  a  source  of  heat,  to  illumination,  to  chemistry,  mechan- 
ics, or  practical  medicine,  The  concoars  will  remain  open  for  five  years, 
dating  from  April  18,  1866. — Med.  News,  Aug.,  1866, /rom  Med.  Times  and 
Gaz. 
Prepared  Liquid  Glue. — Take  of  best  white  glue  sixteen  ounces  ;  white 
lead,  dry,  four  ounces  :  rain  water,  two  pints  ;  alcohol,  four  ounces.  With 
constant  stirring  dissolve  the  glue  and  lead  in  the  water  by  means  of  a 
water-bath.  Add  the  alcohol,  and  continue  the  heat  for  a  few  minutes. 
Lastly  pour  into  bottles  while  it  is  still  hot. — Drug.  Cir.,  Oct.,  1866. 
Marine  Glue. — Dissolve  three  parts  of  India  rubber  in  thirty-four  parts 
of  coal-tar  naphtha — aiding  the  solution  with  heat  and  agitation  ;  add  to 
it  sixty-four  parts  of  powdered  shellac,  which  must  be  heated  in  the  mix- 
ture, till  the  whole  is  dissolved.  While  the  mixture  is  hot  it  is  poured 
upon  metal  plates  in  sheets  like  leather.  When  required  for  use,  it  is 
heated  in  a  pot,  till  soft,  and  then  applied  with  a  brush  to  the  surfaces  to 
be  joined.  Two  pieces  of  wood  joined  with  this  glue  can  scarcely  be  sun- 
dered.— Drug.  Cir.,  Oct.,  1866. 
Preservation  of  Wood  against  Decay. — >A  correspondent  furnishes  us  an 
interesting  article  on  the  above  subject,  which  want  of  space  this  week 
obliges  us  to  condense.  We  merely  give  the  important  parts.  After 
speaking  of  the  advantages  of  charring  wooden  posts  before  setting,  he 
says  : — Scientific  men  have  explained  this  superiority  to  reside  in  the 
peculiarity  of  charcoal  for  absorbing  the  gases  arising  from  decaying  sub- 
stances. But  charcoal  retains  this  property  but  a  short  time  unless  kept 
from  the  air.  The  reason  of  this  lies  in  its  limited  absorbing  power.  In 
less  than  twenty-four  hours  after  being  set,  the  charcoal  becomes  saturat- 
ed, and  is  then  entirely  ineffective  for  protecting  the  wood.  The  cause  of 
the  preservative  influence  must  then  be  sought  elsewhere,  and  the  follow- 
ing is  my  belief: — The  microscope  reveals  the  cause  of  decay  as  due  to 
parasites  feeding  on  albuminous  substances.  Dr.  Schmoele  gives  the  fol- 
lowing conditions,  all  of  which  must  be  fulfilled  before  decay  takes  place: 
The  presence  of  parasites  or  germs,  albuminoids,  moisture,  free  oxygen, 
together  with  a  suitable  temperature,  And  the  absence  of  greater  counter- 
acting influences.  Now,  charring  wood  dispenses  with  the  two  first  condi- 
tions, for  the  heat  required  to  char  the  outside  coating  is  more  than  suffi- 
cient for  decomposing  the  albuminous  substances,  and  destroying  all  para- 
sitic germs.  A  temperature  but  little  above  the  boiling  point  would  an- 
swer for  this  equally  well.  I  come  then  to  the  conclusion  that,  for  pre- 
serving wood,  charring  is  quite  superfluous,  a  much  less  heat  answering 
equally  well.  On  this  idea,  original  I  believe  with  myself,  and  which  I 
claim  as  my  invention,  I  base  my  plan  for  the  preservation  of  wood.  I 
propose  to  store^the  timber,  of  whatever  description,  in  large  stone  or  iron 
