THE  GUMS  AND  RESINS  OF  COMMERCE. 
71 
the  finest  division  of  the  product,  and  may  be  employed  with  the 
greatest  success  for  polishing  plate  glass  and  the  glasses  used  by 
opticians,  without  any  previous  washing. 
The  trials  which  have  been  made  of  this  colcothar,  in  the  arts, 
for  polishing  metals,  principally  gold  and  silver,  have  demonstra- 
ted that  the  finest  polish  may  be  obtained  without  even  scratch- 
ing the  surface,  therefore  it  may  be  employed  for  polishing 
Daguerreotype  plates,  telescopes  and  other  objects  of  that  kind. 
Moreover  artizans  have  found  that,  by  employing  this  colcothar. 
the  operation  of  polishing  glasses  is  very  greatly  accelerated. 
Chemist,  Nov.,  1855,  from  Jour,  de  Pharm.,  July,  1854. 
THE  GUMS  AND  RESINS  OF  COMMERCE. 
By  P.  L.  Simmonds. 
The  subject  which  I  have  undertaken  to  open  up  for  discussion 
this  evening,  is  one  embracing  so  many  important  articles  of 
commerce,  and  extending  over  so  wide  a  field  of  research,  that  I 
can  scarcely  hope  to  do  common  justice  to  any  even  of  the  great 
classes  into  which  it  naturally  divides  itself — much  less  to  enume- 
rate or  particularize  one-half  of  the  various  new  gums  and  resins 
which  I  should  desire  to  bring  more  prominently  into  notice. 
Any  one  of  these  gums  or  resins  would  have  formed  ample  field 
for  investigation  and  inquiry  of  itself,  taking  it  in  its  several  re- 
lations of  origin,  sources  of  supply,  mode  of  procuring,  quantity 
obtainable,  price,  chemical  composition,  and  probable  utility,  as 
compared  with  other  similar  exudations  and  their  commercial 
uses. 
But  in  taking  a  rapid  survey  of  the  whole  group  of  gummy 
and  resinous  exudations,  any  such  close  and  full  description 
would  be  utterly  impossible — and  as  it  is,  I  shall  have  to  pass 
over  much  of  the  information  I  have  arranged,  leaving  it  for  the 
quiet  perusal  and  future  consideration  of  those  who  feel  greater 
interest,  in  its  more  extended  form  in  the  columns  of  the  Society's 
,  Journal. 
In  the  mode  of  treating  my  subject  I  hesitated  at  first  as  to 
whether  it  might  not  be  useful  to  go  over  each  quarter  of  the 
globe  separately,  giving  distinct  accounts  of  the  gummiferous 
plants  and  products  of  Europe,  Africa,  Asia,  Australia,  and 
