118 PARA RUBBER. 



The cylinder is then rotated horizontally at the rate of about 180 

 revolutions per minute for about H minute, after which the speed 

 is reduced to about 100 revolutions per minute for the next 3| 

 minutes. The coagulated latex accumulates in the centre, and the 

 watery portion remains in the outer part between the vertical plates 

 and the wall of the cylinder. When the watery portion is clear the 

 separation of the rubber is considered to be complete, and the 

 coagulated latex is removed. The freshly-coagulated mass is, as 

 shown on Plate 22, in the fresh state very spongy and is torn into 

 irregular pieces, which are pressed between the rollers of a mangle. 

 A figure of the mangle used and the cakes obtained is shown on Plate 

 23, Series A; the irregular cakes, obtained by passing the spongy 

 mass through the rollers, are then cut into worm-like threads by 

 means of shears worked by hand; the "worms" are next placed 

 on wooden shelves to dry. The rubber so prepared may at 

 first contain most of the ingredients present in the latex, the soluble 

 portion of which may be partially removed by repeatedly washing 

 the rubber during the rolling process. Two analyses of this 

 rubber are given elsewhere. 



Mathieu's Apparatus.* 

 An apparatus for coagulating rubber in large quantities by means 

 of heat alone has been considered by Mathieu, which follows in prin- 

 ciple the manipulation of the latex as practised by the Brazilian 

 seringuero. As far as I can understand it, the apparatus is devised 

 to subject thin films of the latex to the action of a surface heated to 

 a constant degree, and can be worked in situ or be put on wheels 

 and transported to any part of the estate where collecting operations 

 are being carried out. Dickson's drying and coagulating machine 

 is described in Chapter XL of this book. 



Tropical Agriculturist. 



