Popular Science Monthly 



557 



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. 



