202 
also  evident  that  the  yield  of  the  Caslilloa  depends  much  more  on 
soil  and  climate  than  has  been  hitherto  supposed. 
Dr.  Tkimkn,  the  Superintendent  of  the  Botanical  Gardens  in 
Ceylon,  gives  the  following  results  from  trees  grown  in  that  island  : — 
Age  of  Tree. 
Yield  of  Latex. 
Lbs.  Oz. 
Per  Cent,  of  Rubber 
IN  Latex. 
Hard  Rubber. 
Lbs.  Oz. 
Six  years 
I 13 
26 
0 T5 
Seven  years 
2 5 
26 
0 9*6 
Eight  years 
3 I 
to 
0 14-2 
Eleven  years  .. 
5 3 
31 
I 97 
These  results  bear  out  the  statements  so  often  made  by  those 
acquainted  with  Ceylon  that  the  Castilloa  cannot  be  profitably 
grown  there,  owing  to  shallowness  of  the  soil  and  the  underlying 
rock  bed.  It  may  be  that  the  climatic  conditions  are  also  unfavour- 
able, so  that  planting  of  the  Castilloa  has  in  many  cases  been 
abandoned. 
Another  cause  which  undoubtedly  greatly  affects  the  yield,  or  at 
least  the  free  flowing  of  the  latex,  is  the  amount  of  rainfall  in  the 
season  preceding  the  tapping.  The  fall  of  rain  during  the  wet 
season  of  1902  was  up  to  the  beginning  of  November  not  over  50 
per  cent,  of  the  rainfall  in  normal  years.  It  is  stated  on  reliable 
authority  that  so  small  a rainfall  has  not  been  known  for  the  past 
20  years.  I am  speaking  of  the  central  parts  of  Vera  Cruz  and  the 
adjoining  state  of  Oaxaca,  though  I believe  the  same  paucity  of  rain 
was  remarked  in  other  parts.  Clearly  owing  to  this  deficiency 
of  rain,  many  large  trees  on  the  property  which  in  former  years 
yielded  abundantly  gave  not  more  than  half  the  former  amount 
obtained,  the  milk  running  sluggishly  and  coagulating  rapidly. 
The  principal  yield  was  thus  furnished  by  the  grenia  (the  rub- 
ber which  dries  on  the  cuts  on  the  trees).  As  an  instance  of 
this  from  13  trees,  averaging  in  circumference  33  inches,  I 
obtained  only  126  ounces  of  milk,  which  gave  me  3 lbs. 
3 oz.  of  rubber,  or  42  per  cent.,  while  the  grenia  collected  from  the 
trees  amounted  to  5 lbs.  12  oz.  ; total  8 lbs.  15  oz.  It  was  my 
intention  to  tap  all  these  trees  a second  time,  but  the  bad  weather 
of  December,  when  the  heaviest  rains  in  the  year  fell,  and 
subsequently  other  occupations  prevented  me  from  making  the 
desired  experiment.  But  I am  firmly  con\  inced  that  a triennial 
tapping  can,  with  perfect  safety,  be  carried  out,  the  trees  in  no  way 
suffering  if  sufficient  time  be  allowed  to  lapse  between  the  two 
operations. — George  C.  Pearson,  in  the  Modern  Mexico  for 
April,  1902. 
CAUSES  OF  THE  DETERIORATION  OF  CONGO 
RUBBER. 
By  G.  Van  den  Kerckhove.  {Anhvevp.) 
In  connection  with  the  conditions  now  existing  in  the  rubber 
trade  of  the  Congo  region,  allow  me  to  state  that  there  are  several 
causes  which  underlie  the  rise  or  decline  in  the  value  of  all  crude 
