Page:Popular Science Monthly Volume 91.djvu/102

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��Popular Science Monthly

���the operator then presses another button to return the money to the caller, just as in other pay- telephone systems.

This accessory has a credit fea- ture, however, which is unusual. In case the tenant is out of change, the operator releases a brass check of the size of a nickel from the coin box. The tenant uses this, and when the manager comes around to collect the coins deposited, the tenant redeems these from him.

���The tenant depos- its a coin in a slot just as in a public telephone. This is carried to the coin box when the con- nection is made

��GERMS HELD UP BY JET OF DRINKING CUP

��Changing the Apartment Telephone into a Pay-When-You-Call System

ANEW telephone device deserves a Carnegie medal for furthering the cause of universal peace between tenants and apartment house managers. It enables the manager to collect at the time of the calling, and protects him and the tenant as well from being over- charged.

The coin-collecting device works entirely independently of the regu- lar telephone system. Thus, the tenant calls the operator's switchboard in the apartment house lobby and is connected with central just as usual. But before the operator ac- tually connects the tenant with central, she connects the coin- collecting box in the tenant's apart- ment with a recording box on her switchboard prefacing the action with a request for "Five cents, please." The recording box signals her the instant the nickel is placed in the collecting box. If central obtains the person called, the opera- tor then connects him with the tenant, and by pressing a button, deposits the nickel in the coin box. If the person called cannot be found,

��Be Thou Wary of the Bubbling Cup

APR9FESSOR in a western university has discovered that small organisms lodge in a great many kinds of bubbling-cup drink- ing fountains, and for a curious reason based on an ancient physical principle.

Twenty-five years ago writers of textbooks on physics had not the wealth of material to draw from that is now available. In carrying out one of their few experiments a rubber-tube-and- spout arrangement was prepared in such a way that it could be attached to an ordinary water faucet and a small jet of water was projected directly upward. In this jet a small ball would be placed — and, curiously enough, would remain in the air, almost stationary, held up by the jet. The jet seemed to clutch the ball and hang onto it instead of throwing it away. The stream would divide under the ball, come up equally on all sides and hold it in place. The sphere might oscillate up and dtown slightly, but otherwise it appeared to be settled per- manently in place. The western professor men- tioned has dis- covered that ba- cilli may oscillate up and down in some kinds of bubbling cups all day long, day after day — in the same way and for the same reason that the sphere did in • the old-time jet.

���The principle

in accordance

with which the

ball is held up

in the jet

of water is the

same as that of the germs

held in the bubbling fountain

�� �