Page:Popular Science Monthly Volume 90.djvu/593

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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.

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