700 



Popular Science Monthly 



Beware ! The Tanks are Coming— 

 Under the Table 



OUR picture shows a toy tank with its 

 young commander. This is a most 

 realistic toy, although it is very inex- 

 pensive. The sides and body are made 

 of wood, and the gun turrets are 

 merely other scraps of wood 

 nailed to the sides. The gun 

 ports are drilled obliquely 

 so that the guns point 

 forward. Ordinary pa- 

 per cigarette holders 

 serve as guns — fired 

 in a most realistic 

 manner by inserting 

 fireworks into them. 

 These toys have no • 

 motive power, as they 

 are primarily intended 

 for the very little folks, 

 but they make fine stage 

 properties in sanguinary 

 play-room battles. They 

 are not dangerous even 

 for youngsters. 



of the shoes and tacked or screwed down. 

 The illustration shows a pair of shoes 

 thus metal-soled and heeled and the tools 

 used in doing the work. It is scarcely 

 necessary to state that both the British 

 and the French authorities encourage 

 this economy in shoe materials. 



Here is the toy tank in full ac- 

 tion. Note the gun being fired 



Novel Idea of Converting Shell-Cases 

 into Shoe Protectors 



TRENCH life is extremely hard on 

 shoeg. That has been definitely proved. 

 Rough usage and exposure to mud and 

 water quickly wear them out. For a long 

 time the men in the trenches have tried to 

 devise some method of prolonging the 

 life of soles and heels. It was a bright 

 and happy idea of 

 some French soldier 

 to use discarded shell- 

 cases to strengthen 

 the heels and soles of 

 his shoes. The plan 

 proved thoroughly 

 practical, and soon 

 many other French 

 and British soldiers 

 imitated the example 

 of the inventive poilu. 

 The shell cases are 

 cut open lengthwise 

 and rolled flat. Then 

 the soles and heels are 

 cut out with strong 

 shears to fit the shape 



A pair of shell-soled trench shoes and 

 the tools used in doing the job properly 



Why Isn't It Hotter Nearer the 

 Sun Than Away From It? 



WHY is the air gen- 

 erally much 

 colder a mile above the 

 earth than near the 

 ground? The heat of 

 the atmosphere comes 

 from the sun, 'but by 

 a somewhat indirect 

 process. The incom- 

 ing sunbeams are only 

 slightly absorbed by 

 the dry air at high levels, 

 and so have little effect 

 on its temperature. In 

 the lower regions of the 

 atmosphere there is al- 

 ways a considerable 

 amount of water vapor 

 (water in the form of gas), and this sub- 

 stance has a relatively large capacity for 

 absorbing heat from sunshine. Lastly, 

 the earth absorbs all the heat that falls 

 upon it, and then gives it back, by radia- 

 tion or conduction, to the air above it. 

 Thus the atmosphere is mainly heated 

 from below and not from above. Air 

 heated near the ground tends to rise, but 

 it cools rapidly in rising. As it 

 reaches higher levels 

 the pressure upon it 

 is less; it expands, 

 pushing away the sur- 

 rounding air, and it 

 uses up in this work 

 some of the energy 

 that it originally pos- 

 sessed in the form of 

 heat.This process is re- 

 ferred to by scientists 

 as "adiabatic cooling." 

 This explains why 

 the heat of summer 

 often seems to come 

 up from the ground, 

 rather than from the 

 boiling sun above. 



