Page:Popular Science Monthly Volume 92.djvu/760

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��Popular Science Monthly

���which makes it possible to use the in- vention as a roof-ladder, or in place of a trestle without extra braces to prevent the spreading of the ladder at the bottom. The ladder may be used either as an ordi- nary extension ladder or as a step-ladder and its rigidity enables it to stand the most severe tests.

��This ladder will not slip, buckle or collapse

A Safe Ladder Appears. You Can't Break Its Rungs

CHARLES J. BROWN, of River Falls, Wis., is the inventor of a new ladder which combines many advantages and novel features. His ladder is light yet strong, and its rungs, which are of metal, are so fast- ened to the wood- en rails of the lad- der, that the struc- ture becomes per- fectly rigid.

The rungs have a flat tread which prevents the foot from slipping. Safety devices are provided, which prevent the slip- ping of the lower end of the ladder on smooth or un- even ground, and the slipping side- ways of the upper }^''^. '"^^'^j^s

J rni • \ IS Simplified

end. There IS also by this recent

a locking device, invention

��Chemicals and Machines Supplant Men In This War

THIS is the most scientific war ever fought. There is less dependence on man-power and more on machinery than at any time in the history of the world. We pin our faith to high explo- sives, poison gases, tear shells, gas masks, liquid fire, etc., all of which are applied chemistry, and to machine guns, heavy artillery, automobiles, submarines, air- planes, and so forth, which are very much refined mechanics. The greatest minds in the scientific and mechanical world have pooled their brains and obtained wonderful results.

���Place-Finding on Maps Is Made Easy by New Device

THE system of using index letters and numbers to enable one to find any spot on a map by referring to an in- dex has been am- plified by a device primarily designed for wall-maps, but could doubtless be adapted to smaller ones too. A rod slides along the top edge of the map and carries a movable indicator. The in- dicator is first ad- justed to the prop- er place on the side index, and then the rod is moved along until it coincides with the correct letter or figure on the top index. The indicator then automatically points to the de- sired place.

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