7i6 



tb:e popular science monthly. 



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 supe- 

 riority 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 ob- 

 ject. 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 

 I'equire 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 mus- 

 cles in question can be strengthened and 

 improved." 



Indnstrial Uses of Mica. — Mica has the 

 invaluable properties of being proof against 

 the attacks of every acid, totally incombus- 

 tible, and impervious to the action of air 

 and water, and of being indefinitely divisible 

 into thinner and thinner plates. In conse- 

 quence of these properties it is applicable 

 to a great variety of purposes, and much 

 attention has recently been given to its in- 

 dustrial use. Its manufacture into various 

 articles has been carried on at Max Rapha- 

 el's establishment in Breslau, Germany, for 

 nineteen years, and has been constantly 

 marked by improvements and new applica- 

 tions introduced from time to time. Its 

 transparency makes it highly available for 

 the glazing of microscopic preparations and 

 the preservation of plant specimens. In Eng- 

 land it is employed in the windows of ma- 

 chine-shops, where glass is liable to be 

 broken by splinters of metal. More recent- 

 ly it has been employed in the membranes 

 of phonographs and the diaphragms of tele- 

 phones. Tablets of it are frequently insert- 

 ed in the doors or walls of smelting-fur- 

 naces, 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 con- 

 ductor 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 sub- 

 jected to an extreme exposure, while the 

 cheerful light ©f 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 col- 

 ors. 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 var- 

 nished, when very fine effects may be pro- 

 duced. The mica brocade is now preferred 

 to the brocades formerly made with bronze, 

 because it is not affected by the sulphuret- 

 ed 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 Moham- 

 medan communities exhibit in respect to 

 particular numbers. In Morocco, five is an 

 object of terror, and it is not permissible, 

 says Hoft, 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 origi- 

 nated in the fact that the hand, which may be 



