Page:Popular Science Monthly Volume 26.djvu/734

716 be made a point of physical excellence in all athletic contests? The example might be fitly set by the volunteers, who might thereafter in time diminish the diameter of the bull's-eyes of their targets; and it would soon be followed by common schools and by athletic clubs. The tests would be easy of application, the value and uses of superiority would be unquestionable. A first effect would be to make people understand what they ought to be able to see, and a counteracting influence would be brought to bear against those conditions which at present render it difficult for the dwellers in large towns ever to look at a distant object. Important good results would not be immediate, nor could they be fully attained except in more than one generation; but I think it can not be doubted that they would ultimately follow. . . . The games which require close attention to a flying object, such as tennis, battledoor and shuttlecock, and in a less degree cricket, are among the most powerful agencies by which the muscles in question can be strengthened and improved."

Industrial Uses of Mica.—Mica has the invaluable properties of being proof against the attacks of every acid, totally incombustible, and impervious to the action of air and water, and of being indefinitely divisible into thinner and thinner plates. In consequence of these properties it is applicable to a great variety of purposes, and much attention has recently been given to its industrial use. Its manufacture into various articles has been carried on at Max Raphael's establishment in Breslau, Germany, for nineteen years, and has been constantly marked by improvements and new applications introduced from time to time. Its transparency makes it highly available for the glazing of microscopic preparations and the preservation of plant specimens. In England it is employed in the windows of machine-shops, where glass is liable to be broken by splinters of metal. More recently it has been employed in the membranes of phonographs and the diaphragms of telephones. Tablets of it arc frequently inserted in the doors or walls of smelting-furnaces, to permit a view of what is going on inside without exposure of the eye. The dials of compasses and the window-lights of war-ships have been made of mica, to avoid the shattering of glass by the cannon-shots of hostile vessels. The mineral has been found extremely valuable for incombustible lamp-shades and screens. Being a poor conductor of heat, mica has been applied with great advantage to use in screens to be placed before open fires, by the aid of which the heat is more evenly distributed through the room without any part of it being subjected to an extreme exposure, while the cheerful light of the fire can be enjoyed at the same time without inconvenience. One of the most valuable applications of mica has been found in the making of spectacle glasses from it, to be worn by workmen in foundries, machine-shops, and other places where hot metal has to be handled, or where the eyes are exposed to the intense glow of the furnaces. Mica in small scales or coarse powder is worked up into a mica brocade or pearl-glazing, for the decoration of articles of fancy. These goods are made in silver and other colors in considerable quantities, at shops in several German towns. The silver brocade is the natural white mica, pounded up, treated with hydrochloric acid, washed, dried, and assorted into grades of fineness by passing it through sieves. The colored varieties are dyed with aniline colors. The mica is applied to the articles it is intended to ornament by sprinkling it upon them, after they have been covered with gum, or a sticky earth, and then varnished, when very fine effects may be produced. The mica brocade is now preferred to the brocades formerly made with bronze, because it is not affected by the sulphuretted hydrogen in the atmosphere, by which the latter always, sooner or later, becomes tarnished.

Forbidden Numbers.—Dr. Goldziher, an eminent student of Semitic lore, remarks upon the peculiar dread that some Mohammedan communities exhibit in respect to particular numbers. In Morocco, five is an object of terror, and it is not permissible, says Höft, to speak of five in the presence of the king; but we must always say four and one, fourteen and one, twenty-four and one, etc. The superstition may have originated in the fact that the hand, which may be