5 68 



tion directed by experience $s. to 4s. per lb, may be secured. The 

 Hevea Braziliensis yields the most satisfactory results on the 

 Amazon and elsewhere, both in quantity and quality of milk. The 

 climatic conditions favourable to its development are — a hot damp 

 atmosphere, with the greatest possible amount of saturation, and a 

 fairly dry warm soil. Excessive flooding is liable to cause "wet 

 feet," thus preventing the growth of the tree and oftentimes prov- 

 ing fatal to it. 



The trees are tapped when upwards of 8 to 10 years old. The 

 incisions are usually made in a series of V-shaped channels con- 

 nected with each other by a horizontal channel about f inch deep 

 by f inch wide. These must be most carefully cleansed and freed 

 from any particle of sand, bark, vegetable fibre or grit of any kind. 

 The collecting cups and cans also must be perfectly clean, for 

 cleanliness is really the first care, and upon its du2 observance 

 depends largely the resulting product. The rubber manufacturer 

 must have his raw material absolutely clean, and to secure this 

 result the rubber is subjected to a process of rolling and heating 

 and tearing between grooved friction rollers under a stream of 

 water which washes away the foreign matter. Growers should 

 always remember that the value of the rubber to the manufacturer 

 is the value of the weight of the washed product, not of the raw- 

 gum, as imported. In this connection we may mention that Para 

 rubber will lose from 5 to 15 per cent, in weight, whilst some badly 

 collected rubbers will lose as much as 50 to 70 per cent. The evil 

 effect of this introduction of foreign matter is not limited to the 

 corresponding loss of weight, for the necessary heating, tearing 

 and rolling the rubber tends to weaken the gum, to reduce its ten- 

 sile strain and to break up its fibres, thus often causing a loss of 

 the vitality of the rubber of from 5 to 25 per centage of foreign 

 matter removed. 



Most unfortunately the otherwise good rubber of Rangoon and 

 Assam contain 20 to 30 per cent, of barky matter, which render 

 them unsuitable for the higher classes of work, as oftentimes some 

 of these particles eventually find their way into the manufactured 

 article. The waterproofing of a garment, the insulation of an 

 ocean cable, or indeed any fine work may be rendered us< less by 

 the presence of these particles. In the case of a cycle inner tube, 

 the grain of sand may become embedded in the thin structure of 

 the tube, inflation causes this grain to "pop" out, subsequent infla- 

 tations extend this point of fracture into a bubble which eventually 

 bursts and spoils the tube. And yet all these difficulties could so 

 easily be avoided by the exercise of due care in collection. It 

 would not cost the collector much to make a practically clean rub- 

 ber, whereas, on the other hand, the increased profit obtained 

 thereby would be considerable. A few years ago the Congo rubbers 

 were carelessly collected and realised barely is. ^d. to is. 6d. per 

 lb. Now by careful collection good prices can be obtained, in 

 some cases as much as 4.V. to 4^. 3^. per lb. Cape Coast kinds have 

 advanced from the same cause, whilst on the other hand many 

 brands have decreased in price from careless and imperfect collec- 



