Page:Popular Science Monthly Volume 91.djvu/588

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��Popular Science Monthly

��from cotton. The coating is composed principally of soluble cotton. In the process the cotton is separated from foreign particles and washed. It is then nitrated, as it is called, which means that it is treated with a mixture of nitric and sulphuric acid and dried. In this form it is gun-cotton — the most powerful ex- plosive known.

Gun-cotton can be dis- solved in certain ethers and alcohols, as well as a few other solvents. Thus dissolved, it ceases to be a violent explosive and be- comes a sticky liquid, the body of which depends on the proportion of the cotton to the solvent.

This solution of cotton is technically called "pyroxylin." It is an indispensable material in many industries. With- out it gas mantle dips, bronzing liquids, liquid court plaster patent leather finishes, wood and metal lacquers and en- amels could not be made cheaply.

In preparing leather substitutes pyroxylin of proper body is mixed with vegetable oils to impart elasticity; min- eral pigments are added to give the desired color. The pyroxylin is applied to dyed cloth as it moves through a coating ma- chine. A thin film is thus spread on the cloth from which the solvent evaporates. As the cloth passes through the machine, which is about one hundred feet long, it dries quickly. Again and again it is passed through the machine until the film is built up to form a coat- ing of the required thickness, toughness and elasticity. The coated cloth is then passed between hot emboss- ing cylinders of steel which press the coating so that it assumes the appearance of morocco, seal, walrus and other leathers. The resultant product looks, feels and wears

���The material from which this hand-bag is made looks, feels and wears like leather and to all intents and purposes it is leather

��like leather, and to all intents and purposes, it is leather.

Very little morocco, seal and walrus leather actually comes from the animals whose hides are so character- istically marked. Most of it is split cowhide embossed in the manner described. That fine looking "seal" pocketbook which you admire in a shop window is nothing but dyed and embossed sheepskin. Only an expert could tell that the product is not what it purports to be. The principal difference is not in the appearance but in the price.

����Only an expert could tell that the "leather" of the upholstery is a substitute

��If You Had No More Teeth Than an Elephant You Couldn't Be a Soldier

IF you have ever had the op- portunity to look inside an elephant's mouth you have your own personal opinion about the reason why it grows a trunk so long that it covers the mouth com- pletely and conceals the interior even when the mouth is open. For the elephant is shy of teeth. There are none at all in the front and only eight — two molars above and two below on each side — in the whole cavernous- mouth. Each of these molars is as large as a man's hand. The hay and fodder which make up the elephant's food are shifted over them by the queerest, ugliest tongue im- aginable. The tongue is lit- erally hung at both ends, having no power of move- ment except in the middle where it shifts back and forth from side to side, arching up against the roof of the mouth like a huge wrinkled pink serpent.

The elephant's baby teeth usually fall out when the animal is about fourteen years old.

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