Page:Popular Science Monthly Volume 90.djvu/573

 Popular Science Monthly

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��Water Proves to be a Better

Fire Extinguisher Than

Dry Powder

DRY fKDwder fire extin- guishers, according to recent analyses made for the British Government, contain as their main constituent, bi- carbonate of soda. Though this chemical gives off a cer- tain quantity of carbon diox- ide when heated, the investi- gating committee doubts whether it has an effective influence on the action of the powder as a fire extinguisher. VVater is said to be far more eff^ective than dr\' powder. An experiment proved that approximately one cubic foot of gas is formed for each pound of dry powder used.

���The see-saw swing ._ _,. _, ^ . __ :..

wheel located in front of the occupants of

��the

��hand- chairs

��How a Giant Redwood Compares with a Locomotive and Train

A GIANT redwood, uprooted and lying prone alongside a railroad engine coupled to eight long passenger cars, as in the illustration below, gives a better idea of the immensity' of these huge trees than any statement of length or diameter in figures. The redwood is in the vegetable world what the elephant is compared to land animals or the whale compared to the other denizens of the deep.

Probably the tallest of these big trees is the Columbia, 294 feet — a hundred yards. Pace off one hundred yards and see what you think of it for the length of a log, and then if you were thinking of sawing or chopping this log, remember that you would have to climb up a ladder and start chopping at a height of thirty feet from the ground, that is, in order to make a cut above the stump of the tree.

These great trees should, in reality, be extinct. But, like the elephant, they continue to live on in an age when their contem- poraries are studied only in the form of fos- sil remains. It is almost im- possible to esti- mate their age.

���A redwood tree uprooted and lying prone beside an eight-car passenger train for size comparison

��A See-Saw Swing Which Children Can Safely Operate

A LARGE swing which children can safely operate has been devised by Edward Hardy, of Blandinsville, Illinois. There is a long cross-beam supported from a high standard. A swinging chair is sus- pended at each end. Located in front of the occupants of the swnng is a handwheel. Turn this handwheel and the swing is operated. Turning the handwheel winds up the cable over the rod with which the handwheel is connected by a series of gears. A downward pull on the free end of the cable causes the swing chair to move inward on the see-saw frame toward the central standard so that one end of the wing becomes lighter than the other and goes up. It is not neces- sary for the occu- pants of the seats to be of equal ag- gregate weight, as the shifting of the chair makes up for any differ- ence.

A half-dozen children can be safely amused for hours by means of this clever contri- vance.

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