Popular Science Monthly 



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that the apparatus could be worked with 

 one hand, leaving the other free to write 

 the characters as they are produced. It 

 is also possible to construct the apparatus 

 in circular form by arranging the troughs 

 around a conical piece and have the 

 balls pushed one at a time up through 

 the center of the cone to fall in one direc- 

 tion or another down the cone and enter 

 one or other of the troughs and then re- 

 turn to the passage in the center to be 

 pushed up again. It is further evident 

 that a magnet might be arranged in con- 

 nection with the above arrangement so 

 that as soon as one ball made a contact 

 after finishing its character the magnet 

 would push up the next ball. Thus the 

 machine would be entirely automatic 

 and the operation continuous. This ar- 

 rangement would make a very effectual 

 apparatus for rapidly learning the code. 



The apparatus, in order to continue 

 to work properly, should be kept clean 

 so that the ball will make perfect contact 

 on the sides of the trough. 



For cheap construction thin shiny tin 

 should be used as this will not tarnish 

 if carefully kept. A better construction 

 is to make the angles of thin brass and 

 have them nickel-plated. Ordinary steel 

 ball-bearings will be satisfactory, but 

 brass balls nickeled are better. 



Home- Made Electric Furnace for 

 Heating with Arc Light 



AN electric furnace of the arc type can 

 1 very easily be made by anyone from 

 the following materials: fire clay, as- 

 bestos fiber and water glass. A mixture 

 of these ingredients will quickly dry and 

 harden into a fireproof mass of low heat 

 conductivity. 



To make the furnace, select a box about 

 8 in. long and 4 in. square. Bore a hole 

 a little above the center of each end just 

 large enough to take a standard lighting 

 carbon. Then mix some of the fire clay, 

 asbestos fiber and water glass together, 

 until a doughy mass is obtained and pack 

 a layer 1 in. thick in the bottom of the 

 box, forcing it down as firmly as possible. 

 Now insert an ordinary glass tumbler in 

 the center of the box and two wooden pins 

 the size of light carbons in the holes at the 

 ends. Around these pack as firmly as 

 possible more of the mixture, filling the 



box completely. Smooth off the top and 

 fill in the small cavities with a mixture of 

 fire clay and water glass alone. In sim- 

 ilar manner make a cover of the same size 

 and about 1 in. thick. Place the box and 



Tumbler 



MiMure ; Tire cloy. Water gloss. Asbestos-'' 



Cross section of the box filled with 

 the mixture around the pins and tumbler 



contents, together with the cover, in some 

 warm place, preferably on the top of a 

 furnace, and allow them to dry for about 

 ten days. At the end of that time the 

 box may be broken away and the pins 

 and tumbler removed. To improve its 

 appearance the outside may be retouched 

 with a little fire clay and water glass. 

 The result is a very efficient arc furnace of 

 practically indestructible material which 

 can be used in series with a suitable re- 

 sistance on any house lighting circuit for 

 many experiments. 



A Simple Way of Cutting Mica 

 V-Rings to Fit on an Armature 



AN armature winder often experiences 

 . much difficulty in cutting a V-ring 

 from a sheet of mica so that it will fit 

 properly. A simple method of getting an 

 exact fit is as follows: We will assume 

 that the bevel surface to be covered with 

 mica is a section of a cone, the apex of 

 which would extend to the heart of the 

 shaft at a point which would be the inter- 

 section of two lines, drawn as the contin- 

 uation of the beveled surface of a V-ring, 

 toward the heart of the shaft. 



First, draw a perpendicular line, A A, 

 on a mica sheet. Measure diameter of the 

 large end of the V-ring with calipers. 

 Place the measurement line, B B, at right 

 with line, A A, taking care that the line, 

 A A, cuts the line, B B, exactly in the 

 center. Next, measure the diameter of 

 the small end, and make the line, C C, 

 parallel to, and at a distance from line 



