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. 



was 



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 



