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Page:Popular Science Monthly Volume 89.djvu/630

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616

��Popular Science Munilily

��Making a Polisher for Table Cutlery from a Piece of Carpet

AN efficient cutlery polisher, as here . shown, is easily made from a small board and a piece of carpet. To a board about 6 in. wide, 8 or lo in. in length and an inch in thickness, with both long edges quarter rounded, is tacked a piece

���Powdered brick is sprinkled between the layers and the articles are rubbed over it

of carpet to entirely cover the board on one side and extend over the rounded edges. Over this carpeted board is placed another piece of carpet the same size as the board, but tacked fast only on one end. The nap surfaces of the two pieces of carpet should face each other. Sprinkle a little cut bath-brick between the layers, moisten knife or fork and rub in and out, as shown in the illustra- tion. — John Hoeck.

��How to

��Make Your Watch-Dial Luminous

��Till' first tiling to do is to procure an ounce of calcium sulphide, lumin- ous. The cost since the war is one dollar an ounce, but you can fix perhajis fifty watches with lliat amount. This ele- ment absorbs light, and after being ex- posed to any bright liglit for five min- utes will glow with a purple light for about four hours.

Remove the cr\'stal fidni the watcli to i)e treated, and willi a pen dipped in shellac go over the numerals and the hands. Some may prefer to make dots onh' at the numerals. Pour out the calcium on a cle.ui piece of paper, clip your finger in it and |)ress some on tlu' moist shellac. Allow about five minutes for it to dry. The calcium not used may ije returned to the bottle.

��Some Peculiarities of Different Styles of Eye-Glasses

WP2ARERS of eye-glasses often give offence to persons whom they meet in the street by looking, and apparently staring at them obliquely in a seemingly critical manner.

The offenders are usually near-sighted persons, who wear the old-fashioned biconcave glasses^, and who ha\e ac- quired a habit of looking obliquely at approaching persons, because they are thus enabled to recognize them at a greater distance. This peculiarity does not seem to be generally known. Far- sighted persons, on the contrary, see less distinctly when they look obliquely through their eye-glasses, if these are of the old biconvex form.

The strength of an eye-glass is inversely proportionate to its focal length and is reckoned in units called diopters. A glass of one diopter has a focal length of one meter, a glass of two diopters has a focal length of one-half meter, and so on. As one meter is nearly equal to 40 inches, the focal length in inches, according to which eye-glasses are still occasionalh' classi- fied, can be obtained by di\ itling 40 by the dioptric number.

The elTecti\e strength of an eye-glass of the old flat form, whether conca\c (Fig. 1) or convex (Fig. 3) is slightly increased and the distinctness of vision is slightly impaired by looking obliquely

���The old flat and convex forms of eye-glasses and the meniscus, or periscopic, glasses

through I 111' perii)lu'ral portion. These (H'ciiliarities are nearly eliminated in the newer meniscus or periscopic glasses ([■'igs. 2 and 4). For far-sighted persons the new curved glasses are always to be reconnnended. Man\- near-sighted persons, on the contiary, |>refer eye- glasses of the old Hat type, which give them distinct direct vision of objects at a moderate tiistance.

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