173 
and  how  in  general  it  behaves  in  the  vulcanising  process  as  com- 
pared with  Castilloa  rubber  in  its  present  day  crude  and  impure 
form,  I have  not  been  able  yet  to  ascertain.  This  work  is,  however, 
in  progress,  and  in  due  course  I will  report  the  results  obtained. 
The  amount  of  resin  in  Castilloa  rubber  shown  above  is  absolute- 
ly unobjectionable,  and  does  not  in  the  least  affect  the  quality  of 
the  rubber.  I am  quite  aware  that  now  and  then  all  sorts  of  sinister 
actions  are  ascribed  to  the  presence  of  resins  in  india-rubber,  but 
there  is  not  the  least  particle  of  evidence  to  show  that  they  are 
intrinsically  detrimental.  As  a matter  of  fact,  in  the  manufacture 
of  quite  a number  of  rubber  goods  resins  are  deliberately  added  to 
the  mixings.' 
O 
It  is  highly  interesting  to  observe  that  the  amount  of  resin  in- 
creases in  the  trees  from  the  root  upwards,  as  the  following  table 
will  show  : — 
RESINS  IN  RUBBER  DRAWN  FROM 
I'runk 
Largest  branches 
Medium  ,, 
Young  " 
Leaves  n ^ ’ 
A similar  increase  is  observed  the  younger 
the  rubber  is  drawn  : — 
Per  cent. 
261 
377 
4*88 
5*86 
7*50 
the  trees  from  which 
RESINS  IN  RUBBER  FROM  TREES. 
Per  cent, 
2 year; 
3 
4- 
5 
6 
8 
old 
42-33 
35*02 
26-47 
i8-i8 
11*59 
7'2  I 
It  will  therefore  be  seen  that  my  advice  not  to  tap  the  trees  un- 
til they  are  at  least  8 years  old  is  not  only  justified  in  the  interest 
of  the  life  and  development  of  the  trees,  but  also  in  the  amount  of 
resin  which  may  safely  be  admitted  in  rubber  of  high  quality. 
There  are  very  few  such  observations  on  the  amount  of  resin  in 
rubber  trees  at  different  periods  of  their  life,  and  in  different  parts 
of  the  tree,  but  it  can  scarcely  be  doubted  that  other  kinds  of  rub- 
ber trees  will  exhibit  similar  conditions,  although  the  amount  of 
resin  accompanying  the  rubber  in  different  trees  appears  to  vary 
not  inconsiderable.  But  they  never  are  entirely  absent,  and  I am  in- 
clined to  think  that  the  usual  view  of  them  as  oxidation  products  of 
the  india-rubber  is  altogether  erroneous. 
Purity. — As  far  as  can  at  the  present  moment  be  seen,  the  fact 
is  amply  demonstrated  that  it  is  possible  to  prepare  from  the  latex 
of  Castilloa  elastica  a rubber  which  for  purity  is  absolutely  without 
a rival,  and  the  physical  properties  of  which  place  it  at  least  on  the 
level  with  the  finest  grades  of  Para  rubber.  And  this  result  is 
obtainable  in  working  upon  the  milk  of  a tree,  which  so  far  has 
only  been  conspicuous  for  yielding  the  worst  of  all  American  rub. 
