A Novel Glass Emptier
If you are given a glass filled with water, and a bottle equally full, and then asked to empty the glass by means of the bottle, and that without emptying the bottle itself, you will imagine you have been set a very difficult task indeed.
Fig. 17.—The glass-emptying bottle.
You will soon see, however, that the solution to this seemingly difficult experiment is quite simple.
First take a cork, and in it pierce two holes. Through these gently push two straws, one being as long as the glass, the other considerably longer ([Fig. 17]).
By means of a pellet of bread or wax close the opening of the shorter straw, and push the cork into the bottle until the water gushes out of the longer straw.
In order to empty the glass it is now only necessary to turn the bottle upside down, in such manner that the little straw touches the bottom of the glass.
Then, taking a pair of scissors, cut this straw very near the end which is sealed.
Immediately the water in the glass will flow out by the long straw until the glass is quite empty, despite the fact that the bottle has remained full all the time ([Fig. 18]).
Now for a few words of explanation, in order to make clear the reason for this unexpected action.
The two straws form the two arms of a siphon, and as they are full of water it is not necessary to remove any air from them.
Fig. 18.—A novel glass-emptier.
As the liquid flows out of the long straw, it tends to produce in the bottle a vacuum. As a vacuum is contrary to nature, it is immediately destroyed by the entrance of an equal quantity of water from the little straw, for the atmospheric pressure exerted on the water in the glass keeps this little straw continually full. In this way all the water is drawn from the glass by the bottle filled with water.