Page:Popular Science Monthly Volume 89.djvu/307

 Popular Science Monthly

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��Straightening Warped Boards

WARI'KI) hoards may bo straight- ened by the following method and they will stay' straight. Resaw the l)oard into strips, about 3 ins. wide. Joint all edges and glue the pieces together, being careful to reverse e\x'ry other piece sidewise. Then plane the surface carcfidl>' and the board will not warp again. — L. G. Abele.

Sloping a Drawing- Board

���An adjustable sloping drawing- board

��THERE is many a mechanic who finds that if his drawing-board were only sloped he could work much better.

The accompanying drawing will ex- plain itself. A block of wood ha\ing three or four headless pins driven in the edge will hold the drawing board, the slope being regulated by the position of the block. — Alfred R. \V.\r.sTAFF.

Keeping Food Without Ice

FOR the temporary' preservation of such food products as rapidly spoil by heat, a modification of the Mexican "011a" is used with success. The "Olla" is a water jar of porous, unglazed native biscuit work, which has the projjerty of keeping the contained water cool, even in the severe temperatures of the southwestern deserts, when filled and hung in a current of air. Hanging in the sun keeps it cooler. The principle invoK't'd is the reduction of temperature due to rapid evaporation, the water which penetrates the clay being rapidly evaporated from the surface of the jar, lowering the temperature of its contents. This principle is applied by dwellers far from an ice supply, as follows:

��A frame of rec|uired size is made fnjin a wood with no decided taste or oilor. The "cucumber" wood, from which the old-fashioned pump-logs were fashioned, is probably the best. Bass or linden is also used. This frame is cov'ered with copper wire screen cloth, using turned copper tacks for fastenings. This again is covered with two or three thicknesses of cheese-cloth, stretched and tacked. A tin gutter is ,so made that a properly designed slot in the bottom may be filled with cotton lamp-wicking, which projects in such manner as to touch the cheese-cloth enclosure, to which it is stitched at intervals to insure positive contact. The floor of this arrangement is elevated in such a way as to permit any excess of moisture reaching the cheese-cloth to drip off and run away to waste. By means of a regulating valve the water supply admitted to the upper gutter is just sufficient to keep the cheese-cloth constantly damp. The entire apparatus should be located in a cool passage or a shady porch. In either case a free circulation of air is essential. The evaporation reduces the temperature inside the device to a noticeable degree.

If a pressure source of water supply is available, it may be used. If not, a bucket can be provided with a prf)per faucet, and furnish the water supply. A collapsible modification of the "Olla" carried by a picnic party will replace the thermos bottle as a means of keeping the liquid refreshments cool.

�� ���Constant evaporation of water from a strip

of cheese-clotli keeps the interior of the

box cool in the hottest weather

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