Page:Popular Science Monthly Volume 92.djvu/853

 Making Soap from Table Refuse

��Popular Science Monthly

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��TO conserve the fats contained in the table refuse and dishwater of the soldiers' mess, the British military authorities installed grease traps. The fat col- lected in these traps averages more than one ounce for each man daily. The trap consists of a tin-lined wooden box, di\'idedinto two compartments by a parti- tion which does not reach the bottorri by about four inches. The dishwater and the table refuse are poured through a strainer into the vat. As the water cools, the fat forms a crust on top and is skimmed ofif.

���Columbia University's fifteen-ton sundial. You can't set this timepiece ahead an hour to save daylight

��This Press Can Make Two Thousand Bricks of Fuel a Day

1"^HE scarcity of coal in all belligerent . countries has imposed upon all na- tions the necessity of exercising great economy in the use of fuels. Long before the war economic reasons made it de- sirable to find some method of utilizing coal dust, sawdust, peat and lignites for heating purposes. Briquettes were in- vented and to some extent used. The war reviv^ed the interest in briquettes, and several new presses for making them were invented.

The device shown in the pic- ture is by a French maker who claims that one of these machines, operated by three men, can turn out from fif- teen hundred to two thousand briquettes daily, each weigh- ing about six and a half pounds. Bri- quettes may be made of coal dust, sawdust, shells of nuts or cacao beans, leaves, peat, etc.

���A fuel-briquette machine which can turn out about two thousand briquettes a day

��Giant Granite Ball Tells Time with Great Accuracy

A HUGE shining ball of green granite, weighing more than fifteen tons, is placed at the edge of the campus of Columbia University, New York city, for use as a sundial. It is set on a solid stone base on the upper surface of which are m.ounted two curved brass plates. The edges of the oval shadow cast by the ball fall along the two brass plates and a comparison w'ill give the correct time. Professor Jacoby, of the astronomy de- partment, has estimated that the degree of inaccuracy of the sundial is never more than a frac- tion of a minute.

The monumental ball was a gift of the class of 1885 to commemorate the twenty-fifth an- niversary of their graduation. Pro- fessor Jacoby, real- izing the possibili- ties of rendering the ball useful as well as ornamental, had the two calibrated plates attached.

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