Page:Popular Science Monthly Volume 89.djvu/486

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472

��Popular Science MontJdy

��Getting a Line on Biddy

���One Nest Sliows the Hen Entering. The Other Shows the Door Automatically Locked

THIS is an illustration of a trap nest — not a guillotine. It is designed to help the poultry breeder to find out his good layers and to keep pedigrees. It is very simple. It may be attached to the underside of the dropping board, with the front facing the pen and arranged so that it can be easily removed. The dropping board will then be the roof of the nest.

The rear of nest may be of wire for the sake of ventilation. If the nest is placed on the wall, slats or wire should be inserted from the front of the nest to the wall at a sharp angle to prevent the hen from roosting on the nest. When she enters the nest, the hen's back raises the door, which releases the catch and allows the door to shut. The catch should be set so that its edge just holds the door, the position being regulated by a screw or nail at the lower inside edge of the catch. A washer on the screw will prevent it from slicking. The guard around the catch holds the nest- ing material away. The nest should be \-isited frequenth' to release the hens.

Boiling Water by Cooling It

Nor a little entertainment can be derived from a burnt-out incan- descent light bulb. The spur of glass on the big end is hollow. \\ hile \()u hoki that |)art under the hottest water in which you can keep \-our hands, care- fully file o(T the point of the bulb. As soon as the water reaches the hollow |>art, it will cnttT and inuiudiati'ly

��begin to boil. This is because the extremely rarefied atmosphere inside lowers the boiling point to the tempera- ture of the water. As soon as the space is filled with steam, the boiling ceases.

Still keeping the opening under water, or closing it with a moistened finger, hold the bulb under a stream of cold water. The boiling immediateK' begins again, because the cold water condenses the steam, thereby lca\ing a partial \acuum.

By closing the opening securely with sealing wa.x when the bulb is about one- fifth full of water, you will have a very novel and interesting toy. When the water has cooled, inverting the bulb sends the water to the other end with a sharp click. In physics, a similar ap- paratus is called a water hammer.

The water can be made to boil at will by heating it gradually in a vessel of warm water, and you can always show how water can be made to boil by cooling. — E. P. Thornton.

To Find Your Depth

THE depth gage illustrated will be found useful for many purposes. It consists of a steel knitting-needle. A, passed through two slots, B C, \n a. sheet of copper, the lower edge of which is perfectly straight. If the metal is placed on a piece of soft wood and in- dented between the slots B (', then turned over and similarly treated above and below the slots, a groove will be formed which will accommodate the needle while holding it with sufiicient grasp to retain any measurements.

���An Indentation in the Metal Forms a Groove in Which the Needle is Grasped

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