Page:Popular Science Monthly Volume 90.djvu/207

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Popular Science Monthly

��This River Is One of Nature's "Find It If You Can" Puzzles

TO him who in the love of Nature holds communion with her visible forms," she often appears as a most incor- rigible tease. She loves to clothe herself in mystery- and propound enighias and puzzles. The Hidden River, in Kentucky, so called because its source is unknown and its outlet undiscoverable, is one of her imagination-exciters. It comes to light for a short distance only, runs turbidly along without ripples or tides over its pale blue waters and vanishes into a cave leading no one knows where.

��Digging War Trenches with a Powerful Tractor

THE present war has been fought with such rapidit\' that in many instances troops have not had time to dig their trenches and barricade them- selves before the enemy made fresh attacks. The demand appeared long ago for a trench-digging tractor, but such a machine did not appear on the European battlefields until recently, when the tractor illustrated work in France. '

It digs a trench as it goes along, just as the common farm tractor plows furrows as it goes along. The earth thrown up on one side serves as the breastworks. The trench-digging tractor is built on a larger scale than any seen in this country. It is said to be doing excellent work for the French.


��The extra leg on tJie ladder prevents it from falling over or slipping, and keeps it steady

A Ladder Which Can't Slip or Fall Over

A LADDER which can be used with equal facility' on a side- hill or in the home has been invented by B. B. Keith of Mansfield, Ohio. It has two additional legs or props, one at each side. This prevents the ladder from slip- ping, and increases its strength. When the ladder is on a level surface both extra legs are used, but when it is used on a hill or on uneven ground only the leg on the down-hill side is necessary as the prop.

���\The that

��powerful tra is thrown up

��trenches just as an ordinary farm tractor plows a furrow. The earth serves as breastworks. It is in use by the French. Soldiers are operating the machine

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