[Illustration:  Can Be Taken from the Cord]

the holes to the outside edge, as shown in Fig. 1.  It is attached to the flexible cord as shown in Fig. 2.  —­Contributed by J.J.  Voelcker; Decatur, Ill.

** Making Photographs on Watch Dials [386]

Beat to a foam the white of an egg, with the addition of a little ammonia.  Add 9 oz. and 3 dr. of water and beat again.  After the egg has settled, filter and let the liquid run over the dial, which has been previously cleaned with ammonia.  When the surplus has run off, coat with the mixture and allow to dry.

A sensitive collodion is now produced as follows:  Dissolve 9 gr. of chloride of zinc in 5 dr. of alcohol; add 7-1/2 gr. of collodion cotton and 6-1/2 dr. of ether.  Shake the whole forcibly.

Dissolve 23 gr. of nitrate of silver in hot water, add 1-1/2 dr. of alcohol and keep the whole solution by heating.  The silver solution is now added in small quantities at a time to the collodion, which must be well settled.  This, of course, is done in the dark room.  After 24 hours the emulsion is filtered by passing it through cotton moistened with alcohol.  This durable collodion emulsion is now flowed thinly upon the prepared watch dial, which, after the collodion has coagulated, is moved up and down in distilled

water until the fatty stripes disappear.  The water is then changed once, and after a short immersion, the dial is left to dry on a piece of blotting paper.  It is now ready for exposure.  Expose under magnesium light and develop with a citrate oxalic developer, or in the following hydroquinone developer: 

Hydroquinone .............1 dr. 
Bromide of potassium .... 6 dr. 
Sulphite of soda......1-1/2 oz. 
Carbonate of soda ....2-2/3 dr. 
Water....................14 oz.

After fixing and drying, coat with a transparent positive varnish.

** Home-Made Overhead Trolley Coaster [387]

The accompanying sketch shows a playground trolley line which furnished a great deal of amusement to many children at a minimum cost.  The wire, which is 3/16 in. in diameter, was stretched between a tree and a barn across a vacant quarter block.  The strength of the wire was first tested by a heavy man.  When not in use the wire is unhooked from the tree and

[Illustration:  Details of the Trolley and How It Is Used]

hauled into the barn and coiled loosely in the hay loft.  The wire was made taut for use by a rope which was fastened to the beams in the barn.  The trolley was made, as shown in Figs. 1 and 2, of strips of wood bolted with stove bolts on two grooved pulleys.  The middle wide board was made of hardwood.  The wheels were taken from light pulley blocks and stove bolts were purchased from a local hardware store to accurately fit the hubs.  As it was necessary to keep the bearings greased, we used vaseline.  This coaster made great sport for the youngsters and at no time were they in danger of a serious fall as the line was hung low and the slant of the wire was moderate.  —­Contributed by H. J. Holden, Palm Springs, Calif.