Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts . strips, or strips of an desired shape of section, corresponding with theform of the grooves. Another method of cutting sheets into Strips is by the use of a large numberof parallel blades mounted on a single moving support. The form of calenders used in the manufacture of sheet gutta-percha is represented in Figs, 2232and 2288. The rolls are 6 feet -1 inches long and 22 inches in diameter, each one weighing about7,000 lbs. They are heated by steam. Gutta-percha tubes arc made by forci

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Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts . strips, or strips of an desired shape of section, corresponding with theform of the grooves. Another method of cutting sheets into Strips is by the use of a large numberof parallel blades mounted on a single moving support. The form of calenders used in the manufacture of sheet gutta-percha is represented in Figs, 2232and 2288. The rolls are 6 feet -1 inches long and 22 inches in diameter, each one weighing about7, 000 lbs. They are heated by steam. Gutta-percha tubes arc made by forcing the gum over a steel mandrel held as a core in a cylinderof iron. As the material is hot on emerging, the sides of the tube would naturally stick together.To prevent this, the tube as fast as it is formed is led through a vat of water some 50 feet in length. GUTTA-PERCHA. 77 The water, pressing equally on the interior as well as the exterior of the tube, keeps it in shape untilit cools and sets. By this means a single tube of nearly 1, 100 feet in length has been made without a break of any kind. 2232.. An important utilization of gutta-percha is as an insulating material for electrical conducting, wires. A thin coating of the gum may be applied to a wire by passing the latter through a vesselcontaining the gutta-percha in a melted state. This method, however, does not answer for applyingthe gutta-percha envelope to sub-marine or subterranean cables.For this purpose the gum is puri-fied with the greatest care, andis placed in a cylinder, where itis kept plastic by heat, and atthe same time is strongly com-pressed by a piston. The wirescomposing the core of the cableare caused to pass through achamber into which the gum alsoenters, and at the same time arerotated, so that they emerge cov-ered with a layer of gutta-percha, which is increased in thickness asdesired by repetitions of the pro-cess. Vulcanization of gutta-perchais effected in the same manner asthat of India-rubber. T