Popular ScieJice Monthly 



577 



Why Navies Have Small 

 Armored Cruisers 



ARMORED cruisers are fast vessels 

 , of from eight to fourteen thousand 

 tons in displacement, which have their 

 vitals, such as guns and machinery, 

 protected by armor plate. They do 

 not carr>' as hea\y guns as battleships, 

 and are supposed to have greater 

 speed. There seems to be a cessation 

 of building of this particular type of 

 vessel in recent years, the main de- 

 pendence in fighting being placed in 

 dreadnoughts, battle cruisers, destroy- 

 ers and submarines. 



Some few scout cruisers are being 

 built by the naval powers. These, as 

 their name indicates, are fast, lightly- 

 constructed cruisers of from five to 

 seven thousand tons displacement, 

 possessing the highest speed attain- 

 able for vessels of their size, great 

 cruising radius, and armed with guns 

 of comparatively small caliber. They 

 are used to locate the enemy and are 

 known as the eves of the fleet. 



Spinning a Top by Means 

 of a Spring 



trig^r;^ The trigger of the burglar trap is so 



/Y deUcately adjusted that the slightest 



movement of the door will operate it 



A DEVICE for spinning 

 a top in a brand-new 

 way has been invented by 

 George John, of Detroit, 

 Michigan. It operates by 

 a spring, which gives the top - 

 its whirling motion as it rapidly unwinds. 



As the illustration shows,, the spring is 

 fitted around a short wooden stem attached 

 in the center of a wooden knob. This stem 

 protrudes beyond the end of the knob so 

 that it may fit into a corresponding hole 

 bored in the center of the top itself. 



When the stem is placed in the hole and 

 the knob is turned, the bot- 

 tom end of the resilient spring 

 is caught by a projection upon 

 the top and the spring winds 

 up. The smaller stem in the 

 knob is then pushed down 

 into one of the several holes 

 bored into the top, to hold 

 it in position. The top is 

 aimed and this stem pushed 

 up. The compressed spring 

 then pushes the top away 

 from the knob while it un- 

 winds. It spins rapidly and 

 with a loud hum. 



COILED COMPRESSION SPRING 



STEM ATTACHED TO HANDLE 



A wound-up spring in the hancic 

 of the top starts the spinning 



Defending the Home with a 

 Mousetrap Gun 



FOR protecting the home against bur- 

 glars, Daniel Cruice, of New York, 

 offers us the home defence "gun," shown 

 in the accompanying illustration. The 

 "gun" uses real gunpowder — not to shoot 

 the offending burglar, but to awaken the 

 sleeping household. 



The contrivance is set by drawing back 

 the skeleton hammer against the tension 

 of its spring and by catching the hammer 

 in the trigger. It is then placed on the 

 floor with its trigger in contact 

 with the door. When the door 

 is opened, the trigger is hit,, 

 the hammer tripped, and the 

 detonating powder fired. No 

 burglar would dare enter 

 after such a noise. Tooth- 

 ed edges prevent the 

 "gun" from slipping back 

 when the door strikes it. 

 Of course the device 

 should not be set untiT 

 all the members of the 

 household are safely in 

 for the night. 



