[Illustration:  Experimenting with a Mirror]

** Miniature Electric Lamps [434]

After several years’ research there has been produced a miniature electric bulb that is a great improvement and a decided departure from the old kind which used a carbon filament.  A metallic filament prepared by a secret chemical process and suspended in the bulb in an S-shape is used instead of the old straight span.  The voltage is gauged by the length of the span.  The brilliancy of the filament excels anything of its length in any voltage.

Of course, the filament is not made of the precious metal, radium; that simply being the trade name.  However, the filament is composed of certain metals from which radium is extracted.

[Illustration:  Types of “Radium” Lamps]

The advantages of the new bulb are manifold.  It gives five times the light on the same voltage and uses one-half of the current consumed by the old carbon filament.  One of the disadvantages of the old style bulb was the glass tip which made a shadow.  This has been obviated in the radium bulb by blowing the tip on the side, as shown in the sketch, so as to produce no shadow.

** How to Make a Magazine Clamp [435]

This device as shown in the illustration can be used to hold newspapers and magazines while reading.  Two pieces of wood are cut as shown, one with a slot to fit over the back of a magazine and the other notched to serve as a clamp.  The piece, A, may be slotted wide enough to insert two or three magazines and made long enough to hold several newspapers.

[Illustration:  Clamp]

** Pewter Finish for Brass [435]

A color resembling pewter may be given to brass by boiling the castings in a cream of tartar solution containing a small amount of chloride of tin.

** Drowning a Dog’s Bark with Water [435]

The owner of two dogs was very much annoyed by the dogs barking at night.  It began to be such a nuisance that the throwing of old shoes and empty bottles did not stop the noise.  The only thing that seemed to put a stop to it was water.

[Illustration:  Water Treatment for Dog’s Bark]

Being on the third floor of the house, and a little too far from the kennel to throw the water effectively, a mechanism was arranged as shown in the sketch.

A faucet for the garden hose was directly below the window.  An 8-in. wooden grooved pulley was slipped over an axle which had one end fitted on the handle of the faucet.  A rope was extended to the window on the third floor and passed around the pulley several times, thence over an iron pulley fastened to the wall of the house and a weight was attached to its end.  By pulling the rope up at the window the large pulley would turn on the water and when released the weight would shut off the flow.  The nozzle was fastened so as to direct the stream where it would do the most good.  —­Contributed by A. S. Pennoyer, Berkeley, Cal.