to  render  its  continued  employment  most  deplorable.  The  coagula- 
tion with  soap  as  practised  in  the  Isthmus  of  Panama  is  barbarous 
in  the  extreme,  and  it  is  not  surprising  that  it  yields  a product  of 
very  bad  quality  indeed. 
Amongst  the  above-named  process  I have  not  enumerated  a pro- 
cess said  to  be  practised  in  Mexico,  and  simply  consisting  in  the 
boiling  of  the  latex  in  earthen  vessels  (jacaras).  If  this  process  is 
actually  used,  it  can  certainly  not  be  carried  out  with  the  fresh  latex 
for  the  simple  reason  that  over  and  over  again  I have  satisfied  my- 
self that  even  on  very  prolonged  boiling  of  the  slightly  diluted  latex 
furnished  by  the  tree  at  Las  Cascadas  no  coagulation  can  be  ol> 
tained.  The  cause  of  this  is  to  be  found  in  the  fact  that  the  aqueous 
vehicle  of  the  latex,  although  it  certainly  contains  a large  amount  of 
albuminous  matter  when  rapidly  separated  from  the  latex  immedi- 
ately after  this  has  been  obtained,  is  of  a very  light  olive  green 
colour  and  even  on  very  prolonged  boiling  does  not  coagulate,  nor 
even  become  turbid.  On  standing  exposed  to  the  air  this  aqueous 
vehicle  very  rapidly  assumes  a darker  colour,  and  eventually  forms 
an  almost  inky  liquid.  This,  on  boiling,  undergoes  immediate  coagula- 
tion, and  a most  copious  deposit  of  insoluble  albumen  is  obtained. 
In  entire  agreement  with  this  observation  is  the  fact  that  if  the 
Castilloa  latex  be  allowed  to  stand  for  sometime  until  it  has  assumed 
a very  dark  colour  it  will  now  be  found  that  on  short  boiling  rapid 
and  complete  coagulation  takes  place.  I have  not  yet  succeeded 
in  ascertaining  the  cause  of  this  curious  phenomenon,  but  it  is  ob- 
vious that  unless  the  Castilloa  latex  obtained  in  Mexico  differs  very 
considerably  from  the  latex  yielded  by  the  same  trees  in  the  Isthmus 
coagulation  by  boiling  in  Mexico,  must  be  preceded  by  an  ageing 
of  the  latex  as  otherwise  no  coagulation  would  take  place. 
It  is  not  very  easy  to  see  that  the  chief  point  in  attempting  to 
prepare  a pure  rubber  from  the  latex  of  Castilloa  elastica,  and  as  a 
matter  of  fact,  from  the  latex  of  any  other  rubber  tree,  must  consist 
in  the  elimination  from  the  rubber,  prior  to  its  ^‘agglutination,  ” of 
all  albuminous  matter.  The  first  step  in  this  direction  is  the  dilut- 
ing of  the  crude  latex  with  water,  of  which  at  least  five  times  the 
volume  of  the  latex  treated  should  be  used.  In  the  case  of  the 
thick,  curdy  latex  yielded  by  the  trees  at  Las  Cascadas  it  is  prefer- 
able to  use  actually  boiling  water,  but  in  how  far  this  applies  to  the 
latex  obtained  in  other  districts  or  from  different  trees  is  a matter 
for  experiment.  Boiling  water  at  once  converts  this  latex  into  a 
thin,  very  fluid  milk  which  through  a common  cotton  gauze  is  strained 
in  order  to  remove  from  it  any  insoluble  impurities  such  as  earth, 
wood,  bark,  and  the  like.  This  milk  is  best  strained  into  thorough- 
ly well  washed  petroleum  barrels.  As  soon  as  the  barrel  is  com- 
pletely filled,  about  8 ozs.  of  formaldehyde  are  added,  the  whole 
well  stirred,  and  allowed  to  stand  for  24  hours.  The  action  of  the 
formaldehyde  appears  to  be  twofold.  In  the  first  instance,  it 
effectually  prevents  any  tendency  of  the  albumen  to  coagulate  in 
the  hot  solution,  and  thereby  to  cause  mischief.  But,  as  compara- 
tive experiments  showed  beyond  any  doubt,  it  also  has  a most 
distinct  effect  upon  the  india-  rubber,  which  collects  on  the  top  of 
