5 1 o  Development  of  the  Chemical  Arts.    { ^"^•^oy'^ij^'"' 
At  the  Opera  House  at  New  York,*  a  diagram  of  about  lo  square 
metres  upon  a  screen  of  damp  muslin  was  lit  up  by  the  aid  of  a  system 
of  powerful  lenses,  whilst  the  lamp  stood  at  the  back-ground  of  the 
stage  at  the  distance  of  25  metres,  and  gave  a  striking  effect.  In  con- 
junction with  this  light  the  magic  lantern  was  adopted  in  America  to 
exhibit  apparatus,  photographs  on  glass,  and  other  drawings  in  large 
lecture-halls,  especially  since  Outerbridge  discovered  the  way  of  using 
thin  plates  of  gelatin  for  the  production  of  lithographs  or  pen-drawings. 
The  effect  is  easily  conceived  if  we  remember  that  the  oxyhydrogen 
flame  is  16J  times  more  brilliant  than  that  of  an  ordinary  burner  fed 
with  the  same  amount  of  gas. 
The  daily  production  of  the  New  York  Oxygen  Company  amounted 
in  1870  to  30,000  cubic  feet,  or  850  cubic  metres.  The  gas  is  deliv- 
ered in  iron  cylinders  (Robert  Grant's  patent,  New  York),  9  inches  in 
diameter  and  30  inches  long,  which  are  filled  with  oxygen  under  a  pres- 
sure of  20  to  30  atmospheres.  The  cylinder  is  sold  at  i  dollar  per 
cubic  foot,  including  the  oxygen  contained  in  it  at  ordinary  atmospheric 
pressure.  The  oxygen,  on  refilling,  is  i:upplied  at  five  cents  per  cubic 
foot  under  the  pressure  of  i  atmosphere,t  an  exceedingly  high  price, 
more  than  twenty-two  times  as  great  as  Kuppelweiser's  calculation,  as 
quoted  above,  although  Tessie  du  Motay's  method  is  in  use  in  New 
York. 
Since  1867  Tessi^  du  Motay  has  attempted  to  apply  the  oxygen  light 
to  streets  and  squares.  The  places  before  the  Tuileries  and  before  the 
Hotel  de  Ville  were  radiant  with  the  light  thrown  off  by  cylinders  of 
zirconj  under  the  joint  influence  of  coal-gas  and  oxygen.  The  fluctu- 
ating nature  of  the  flame  and  the  great  expense  induced  him  to  turn  his 
attention  to  the  carburation  of  hydrogen  and  coal-gas.  These  gases 
were  led  before  entering  the  burners  into  a  vessel  attached  to  each  lamp, 
and  containing  heavy  hydrocarbons.  In  this  manner  the  Boulevards  be- 
tween Rue  Drouot  and  Rue  Scribe  were  illuminated  with  70  oxygen  burn- 
ers. This  method,  also,  was  given  up,  and  a  highly  carburetted  gas  was 
prepared  in  place  of  common  coal-gas,  and  was  burnt  along  with  oxy- 
gen. In  this  new  modification  the  process  was  seen  by  visitors  to  the 
Vienna  Exhibition  at  the  Empress  Elizabeth  Western  Railway  Ter- 
*  Morton,  "Journal  of  the  Franklin  Institute,"  liii,  liv,  Iv. 
f  "Deutsche  Gewerbe  Zeitung,"  1867,  p.  18. 
X  Burnt  zirconia  kneaded  into  a  paste  with  aqueous  boracic  acid,  and  burnt  in  iron 
moulds  at  a  red  heat. 
