PRODUCING  HIGH  TEMPERATURES  BY  COAL  GAS  AND  AIR.  257 
Captain  Burton  further  says  that  "  the  East  African  seaboard 
from  Ras  Gromani  in  S.  lat.  3°  to  Ras  Delgado  in  10°  41', 
with  a  medium  depth  of  30  miles,  may  be  called  the  Copal 
Coast." 
At  Zanzibar  the  resin  is  sifted  and  cleansed  from  impurities 
before  it  finds  its  way  into  the  hands  of  the  foreign  merchants  ; 
after  this  it  is  again  cleansed  by  washing  in  chemical  solutions 
of  various  degrees  of  strength,  care  being  taken  to  thoroughly 
purify,  but  at  the  same  time  not  to  injure  the  so-called  " goose- 
skin,"  or  the  impress  of  the  sand. 
All  parts  of  the  plants  of  the  copal-yielding  species  of  Hy- 
mencea  are  highly  charged  with  resin,  and  in  none  is  it  more 
apparent  than  in  the  fruits  of  the  species  sent  home  by  Colonel 
Playfair.  The  little  warts  or  verrucosities  upon  the  surface  of 
these  pods  are  lumps  of  clear,  colorless  resin,  simply  covered 
with  the  thin  epidermis  or  cuticle  of  the  pod.  To  such  an  ex- 
tent are  these  pods  charged  with  resin,  that  they  burn  freely 
upon  the  least  approach  of  flame.  The  same  property  is  ob- 
servable in  the  pods  of  the  South  American  species,  Hymencea 
Courbaril,  from  the  trunk  of  which  exudes  very  large  quantities 
of  resin  ;  but  this  pod  being  larger  and  mere  ligneous,  and  the 
resin  distributed  in  small  ducts  all  over  the  surface  without 
penetrating  the  substance  of  the  pod,  does  not  burn  so  readily, 
nor  is  the  quantity  of  resin  so  large.  The  outside  of  these  pods 
much  resembles  in  appearance  the  sand-fretted  surface  of  the 
resin. — Loud.  Pharm.  Journ.,  from  G-ardners  Chronicle*. 
ON  PRODUCING  HIGH  TEMPERATURES  BY  MEANS. OF 
COAL  GAS  AND  AIR. 
By  M.  Th.  Schlcesing. 
Chemists  have  not  as  yet  derived  from  coal  gas  all  the  advan- 
tages as  a  source  of  heat  which  it  is  capable  of  affording.  The 
apparatus  used  in  laboratories  gives,  at  most,  the  temperature  of 
white  heat,  unless  the  air  is  replaced  by  oxygen,  as  is  done  by 
MM.  H.  Sainte-Claire  Deville  and  Debray.  By  ascertaining 
the  temperature  produced  by  gas  burnt  with  an  exactly  sufficient 
quantity  of  air,  and  that  produced  simply  by  the  flame  of  a  jet,, 
17 
