472 
VARIETIES. 
length,  with  less  pressure  than  is  required  to  force  it  laterally  through  a 
plank  three-quarters  of  an  inch  in  thickness.  When  the  sap  is  forced  out 
the  preservative  fluid  follows  it,  and  its  presence  at  the  ends  of  the  wood  is 
ascertained  by  a  chemical  test. 
Thus  the  sap  and  fermenting  juices  become  completely  expelled,  and  the 
timber  becomes  saturated  throughout  its  length  with  the  preserving  fluid. 
Important  advantages  arise  in  the  employment  of  this  process  in  this 
country.  First,  it  may  be  applied  successfully  to  Scotch  fir,  beech,  elm, 
and  other  home-grown  timber  ;  secondly,  it  is  not  necessary  that  the  wood 
should  be  dried  or  seasoned  before  being  prepared,  but,  on  the  contrary, 
the  operation  is  best  effected  within  a  few  weeks  after  the  tree  has  been 
cut  down  ;  thirdly,  any  cheap  antiseptic  fluids,  such  as  solutions  of  sulphate 
of  copper,  or  chloride  of  zinc,  become  perfect  preservatives  when  applied 
in  this  manner ;  and,  fourthly,  no  heat  is  required,  and  the  wood  is  not 
rendered  inflammable. 
The  result  is  a  saving  in  first  cost  of  about  one  shilling  per  sleeper  as 
compared  Avith  Baltic  timber  creosoted ;  while  the  durability  thus  attained 
has  been  fully  ascertained  by  the  extensive  trials  already  made  in  France, 
which  will  be  further  described. 
Success  of  the  System  in  France. — The  first  report  upon  this  process  was 
made  in  the  year  1841,  by  a  committee  of  the  French  Academy  of  Science, 
M.  Arago  being  chairman,  upon  the  occasion  of  a  pamphlet  on  the  subject 
by  Dr.  Boucherie  being  read  before  that  distinguished  body,  and  which  was 
consequently  ordered  to  be  inserted  in  the  "  Recueil  des  Savants  Etrangers" 
and  copies  to  be  forwarded  to  the  Ministers  of  Agriculture,  Commerce, 
Public  Works,  Marine,  Finance,  and  War. 
In  the  year  1850,  the  French  government  appointed  a  commission  of  dis- 
tinguished engineers  of  the  Points  et  Chaussees,  and  again  in  1852,  the 
principal  officers  of  Genise,  to  minutely  investigate  and  report  upon  the 
merits  of  this  invention,  and  which  they  accordingly  did  ;  the  reports  on 
both  occasions  being  favorable  to  Dr.  Boucherie's  invention  ;  while,  at  the 
close  of  the  recent  Exposition,  the  French  government  marked  its  sense  of 
the  public  benefit  derivable  from  it  by  awarding  to  its  inventor,  the  rare 
distinction  of  the  large  gold  medal  of  honor,  of  which  there  were  only  four 
conferred  on  the  representatives  of  the  whole  of  France. 
Duration  of  Sleepers  prepared  by  this  Process. — In  the  year  1846,  80,000 
sleepers  thus  prepared,  were  authorized  to  be  laid  down  upon  the  Northern 
Railway  of  France,  together  with  a  certain  quantity  of  unprepared  sleepers. 
In  this  instance,  the  Company  chose  wood  that  decays  easily,  and  which, 
on  that  account,  had  been  rejected  for  durable  works.  They  employed 
beech,  pine,  alder,  elm,  and  birch. 
These  sleepers  were  inspected  every  year,  and  each  time  were  found  in  a 
perfect  state  of  preservation.  In  May,  1855,  Dr.  Boucherie  being  desirous 
of  exhibiting  in  the  Exposition  some  wood  prepared  by  this  process,  had  a 
few  of  each  kind  of  these  sleepers  taken  up,  and  they  were  found  in  every 
