444 
CONSOLIDATED  COAL  DUST. 
We  have  not  before  us  the  data  which  would  render  possible 
such  a  comparison  as  might  explain  the  very  different  success 
attained  in  this  country  and  abroad,  but  we  know  that  in  some 
cases  the  fault  lay  in  the  costly  nature  of  the  machinery  em- 
ployed, and  in  other  cases  it  was  to  be  found  in  the  friable 
nature  of  the  product  obtained,  which  rendered  its  transporta- 
tion troublesome  and  expensive.  We  have  now  before  us  speci- 
mens of  consolidated  coal-dust,  labelled  "  Gerard  fuel,"  and  re- 
markable for  several  peculiarities,  which  makes  us  think  that 
the  process  by  which  they  are  produced*  will  not  share  the  fate 
of  its  American  predecessors.  These  specimens  are  cubical, 
some  of  them  measuring  about  1-5  inch  on  each  edge,  others 
about  four  inches.  They  may  be  thrown  violently  on  the  floor 
without  sensible  injury,  and  are  thus  proved  to  possess  all 
requisite  consistency,  while  their  process  of  manufacture,  which 
we  shall  proceed  to  describe,  looks  well  in  other  respects.  The 
coal-waste  is  carefully  screened,  by  which  means  it  is  stated  that 
30  per  cent,  of  good  coal  may  be  secured.  The  finer  particles 
are  then  crushed  between  rollers  of  chilled  iron,  and  are  then 
mixed  in  a  machine,  much  like  that  used  for  tempering  clay  with 
coal  tar,  steam  being  also  admitted  and  flour  added,  according 
to  the  patent,  but  not  found  to  be  important  in  practice.  From 
the  mixer,  the  hot,  wet,  tarry  dust  passes  into  the  moulder, 
where  plungers  force  it  into  moulds  with  movable  ends ;  so  that, 
when  each  block  has  been  formed,  the  end  is  raised,  and  a  second 
and  further  push  of  the  plunger  throws  out  the  finished  cube. 
The  cubes  so  formed  are  packed  closely  in  iron  boxes,  and  run 
into  an  oven,  where  they  are  heated  to  a  temperature,  which 
distils  off  as  illuminating  gas  all  the  hydrocarbon  of  the  coal  tar. 
From  all  that  has  been  published  abroad  on  the  subject,  it  seems 
that  experience  has  demonstrated  the  efficiency  of  the  following 
points  of  treatment : — 
1st.  The  thorough  pulverization  and  wet  mixing.  2d.  The 
use  of  coal  tar  as  a  cement.  3d.  The  baking  after  compression. 
The  process  just  described  involves  these  points,  and  certainly 
produces  most  excellent  results.  If,  on  practical  trial,  it  shall 
prove  to  possess  the  last  but  all  important  requisite  of  economy, 
it  cannot  but  render  the  manufacture  of  artificial  fuel  here,  what 
