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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 



