THE HEVEA RUBBER TREE IN THE AMAZON VALLEY 35 
Examination of trees tapped with the Amazonas knife shows that 
on an average 16 cuts are made for every 13 centimeters of bark used. 
Tapping a given segment of bark is begun at a height of 150 or 160 
centimeters from the ground; therefore this segment would last at 
least three years and generally longer. With trees tapped on one- 
third of the circumference, a 9-year rotation system could be applied, 
so that the renewed bark should be in excellent condition. It is 
probable that after such treatment most of the trees could be tapped 
with the Jebong knife and still larger yields secured. 
Some rubber is lost as scrap in the cuts from this knife, because 
the cuts are too narrow to permit scraping the cut without undue 
loss of time; but the quantity of scrap left in the cuts is small. In 
leaning trees, latex sometimes flows over the edge of the cut and is 
lost; but in general the loss of rubber is much less than with the 
machadinho, and the use of the knife would be justified on this basis 
alone. The adoption of this knife is one of the steps in the direction 
of more economical production. 
PREPARATION OF THE RUBBER 
Few changes in the preparation of the rubber are to be recom- 
mended. The smoking process used generally in the Amazon district 
is probably the best native method of preparing rubber ever devised. 
It is hard to see how any better method can be applied on the estradas, 
which are always too scattered to support a central factory of any 
size. Various fancy drums, etc., for smoking the rubber have been 
patented and recommended by different people, but none of them are 
so simple as the native method, none are so cheap, and none are so 
good for the purpose they have to serve. Though we now know that 
as good rubber can be produced by other methods as by smoke 
coagulation, there is certainly no other method by which as good 
rubber can be made under the conditions which exist on the estradas. 
The task of smoking the rubber is not a pleasant one; it may 
even be a somewhat unhealthful one, but for the present it must 
be continued until it is shown that another one is as good and costs 
no more. 
One small change in preparing ball rubber is to be recommended. 
As has been said, the ball is begun by wrapping a mass of naturally 
coagulated rubber around a pole, so that sufficient surface is provided 
to begin the formation of a ball. This naturally coagulated rubber is 
sometimes very dirty and is always classed as sernamby. In some 
places the seringueiros start pouring latex over a large block of 
imbauba wood (Cecropia sp.) which has been cut into the form of 
a ball, with a projecting rod at either end. Imbauba wood is very 
easily* cut, so this shaping is not difficult. Over this ball latex is 
poured and smoked until a considerable mass is secured. This layer 
is then cut, pulled off the block, and wrapped on the pole used for 
smoking the rubber, to form a foundation for a ball. When a ball so 
started is completed it consists of nothing but smoked rubber through- 
out and is uniform in quality. Increased care in handling the latex 
at all stages is desirable, so that more of it may be made into fine hard 
Para and less into sernamby. Greater cleanliness of cups has already 
been suggested as a means of reducing the formation of lump. More 
care in keeping the sernamby free from unnecessary dirt and con- 
