202 
also evident that the yield of the Castilloa depends much more on 
soil and climate than has been hitherto supposed. 
Dr. Trim ux, the Superintendent of the Botauical Gardens in 
Ceylon, gives the following results from trees grown in that island : — 
Age of Tree. 
Yield ok Latex. • 
Per Cent, ok Rubber 
in Latex. 
Hard Rubber. 
Lbs. Oz. 
Lbs. Oz. 
Six years 
I 13 
26 
0 7*5 
Seven years 
2 5 
26 
0 9-6 
Eight years 
3 1 
29 
O I4'2 
Eleven years .. 
5 3 
31 
1 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 whioh 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 1 believe the same paucity of rain 
was remarked in other parts. Clearly owing to this deficiency 
of rain, many large frees 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 3 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 convinced 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. •{Antwerp.) 
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 
