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Page:Popular Science Monthly Volume 81.djvu/328

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322
THE POPULAR SCIENCE MONTHLY

the drying out of the shrub and breaking off of twigs. Since it was found possible to increase the field weight by methods devious and of little cost, thus selling stones or water at an exceptional price even in a country where that commodity is not cheap, a control by means of tags was devised, enabling a systematic comparison of the field and factory weights of shrub from all areas. The price of water quickly fell.

 

Manufacture

To keep a large plant running regularly a considerable reserve of shrub must be held. This was formerly stacked in the open, but later, when rapid deterioration was discovered, suitable storage warehouses were provided, thus obviating the deleterious action of the sun. When

PSM V81 D328 Packing guayule rubber at torreon coahuilla.png

Fig. 11. Packing Guayule Rubber at Torréon, Coahuilla.

the shrub is in good condition—that is, sufficiently, but not too dry—the bales are passed out to a washing floor where all dust and soil is removed by a stream of water. The importance of this becomes apparent when it is reflected that the rubber picks up particles of soil and its specific gravity altered, so making the separation of rubber and bagasse more difficult.

The shrub is now run between the steel rolls of a crusher which, running at differential speeds, grind up the plants into torn fragments. Peons take this material up in baskets and convey it to pebble mills. These are short iron cylinders which are arranged so as to rotate on their axes. Each mill is lined with flint bricks and is charged with ground shrub, water and coarse flint pebbles which by their impact on each other comminute the shrub and agglomerate the rubber. After