512  Development  of  the  Chemical  Arts,  {^"i/oTis^s.^""' 
opinion  is  in  flat  contradiction  to  that  of  Schiele  ;*  but  it  agrees  closely 
with  the  report  which  Le  Blancf  a  year  earlier  had  presented  to  the 
municipal  gas  direction  of  Paris. 
This  report  resulted  from  the  minute  investigations  of  MM.  Peligot, 
Lamy,  Troost,  De  Mond^sir,  and  Le  Blanc,  who  had  been  appointed 
as  commissioners  by  the  Prefect  of  the  Seine  in  1869.  They  under- 
took an  examination  of  the  process  in  the  Place  de  I'Opera  as  well  as 
in  the  laboratory.  They  burnt  ordinary  gas,  bog-head  gas,  and  gas 
saturated  according  to  different  systems  with  liquid  hydrocarbons,  along 
with  about  half  its  volume  of  oxygen,  and  making  use  of  various  burn- 
ers. They  came  to  the  conclusion  that,  for  an  equal  intensity  of  light, 
the  process  of  Tess^  du  Motay  is  almost  always  dearer — generally 
twice  as  dear — as  the  ordinary  mode  of  lighting.  In  one  case  only, 
where  the  liquid  hydrocarbons  of  the  Boghead  coal  were  used  for  car- 
buretting  by  absorption,  in  wicks,  according  to  the  plan  of  Leveque, 
over  which  the  gas  passed,  it  was  found  that  the  new  process  was  twice 
as  cheap  as  the  ordinary  method.  This,  moreover,  applied  only  to  the 
use  of  large  burners,  and  the  consequent  production  of  great  quantities 
of  light.  All  the  figures  given  by  Tesse  du  Motay's  Company,  as  to 
the  cost  of  oxygen  and  the  expense  of  carburetting,  were  taken  for 
granted.  In  fact,  however,  it  appeared  that,  in  this  experiment,  i  cubic 
metre  of  gas  took  up,  not  50  grms.  of  liquid  hydrocarbon,  as  the  Com- 
pany stated,  but  266  grms.,  which  rendered  the  economy  of  the  process 
at  any  rate  doubtful.  As  regards  the  strength  of  the  light,  the  com- 
missioners found  it  from  three  to  seven  times  greater  than  that  of  com- 
mon coal-gas.  But  Boghead  gas  in  suitable  burners  can  be  made  to 
*  yield  a  light  three  times  stronger  than  that  of  coal-gas  without  the  aid 
of  pure  oxygen.  For  most  purposes,  moreover,  a  very  great  intensity 
of  light  is  not  desired,  as  we  see  it  reduced  to  30  per  cent,  by  means  of 
glass  shades  and  screens. 
The  conclusion  of  the  commission,  therefore,  was  to  advise  the 
municipality  of  Paris  not  to  permit  the  laying  down  of  mains  for  oxygen 
gas,  but  to  leave  it  to  the  Company  to  furnish  oxygen  and  carbur- 
etted  gas  in  portable  gasometers  to  such  persons  as  required  an  intense 
light. 
The  results  obtained  in  Brussels  were  not  more  favorable.  Lighting 
■"^"Schiele,  Journal  f.  Gasbeleuchtung,"  Jan.,  1873. 
t" Rapport  de  M.  F.  Le  Blanc  sur  lenouvel  eclairage  oxyhydrlque,"  Paris,  1872  j 
also  "Journal  f.  Gasbeleuchtung,"  1872,  641. 
