CONSOLIDATED  COAL  DUST, 
443 
These  all  burn  brightly  and  steadily,  but  the  flame  is  smaller 
and  the  combustion  slower  than  that  of  pure  magnesium.  The 
flame  is  cold,  and  the  heat-conducting  property  of  the  alloy, 
compared  with  magnesium,  is  sensibly  diminished,  showing  the 
change  in  the  molecular  construction  of  the  metal.  The  smoke 
produced  in  the  combustion  of  these  alloys  is  more  dense,  and, 
as  it  curls  gracefully  away,  it  is  seen  to  be  fringed  with  a  rather 
pretty  dark  purple  tint ;  but  the  magnesium  light  is  so  very 
intense  that  it  almost  completely  masks  the  thallium  flame,  so 
that  it  is  not  observable  in  some  of  the  alloys — indeed,  the 
green  light  is  scarcely  recognizable  even  in  an  alloy  containing 
50  per  cent,  of  thallium. 
An  alloy  of  5  per  cent,  of  thallium  appears  to  render  magne- 
sium less  brittle  and  more  ductile  than  pure  magnesium  is 
usually  produced ;  but  the  higher  alloys  of  thallium,  say  those 
containing  25  and  50  per  cent,  of  thallium,  are  more  oxidizable 
than  pure  magnesium. 
The  metals  were  put  together  cold  in  a  closed  iron  crucible ; 
only  a  slow  heat  was  required  to  melt  them.- — Land.  CI  tern. 
Neivs,  May  17,  1867. 
CONSOLIDATED  COAL  DUST. 
Many  attempts  have  been  made  from  time  to  time  to  utilize 
that  material  known  as  coal-waste,  which  in  our  mining  region 
has  been  thrown  aside  until  the  waste  heaps,  so  accumulated, 
have  threatened  to  rival  in  extent  and  elevation  the  natural 
mountains  among  which  they  find  themselves.  Such  attempts 
have  as  yet,  to  the  best  of  our  knowledge,  proved  unsuccessful 
in  a  commercial  point  of  view,  in  this  country,  though  a  very 
different  result  has  been  obtained  abroad.  Thus,  in  an  article  by 
M.  L.  Gruner,  Ingenieur  en  Chef  des  Mines,  which  appeared  in 
the  October  number  of  the  Bulletin  de  la  Societe  d 'Encourage- 
ment p our  T Industrie  Rationale,  it  is  stated  that  in  France  some 
twenty  establishments  are  carrying  on  this  manufacture,  and 
produce  yearly  500,000  tons ;  in  Belgium  some  seven  manu- 
facturers turn  out  400,000  tons,  while  in  other  countries  the 
product,  though  less,  is  very  considerable, 
