The experienced fisherman who smiles at the amateur's restless fidgeting and complaining has discovered by careful observation that the fish who swims around in such an exasperating manner just a foot or so away from the temptingly baited hook has had an advance tip that something out of the ordinary is going on up above him. For sound, whether it be the noise of an oarlock or a companion's casual remark, can be heard more than four times as easily by the fish in the water beneath than it can up above in the air. Sound travels very quickly through the air, traversing ten hundred and ninety feet in a second, but it reaches forty-seven hundred feet away under water in the same time.

When the crowd on the other side of the baseball grounds yells across the field it seems as though we have heard their cheers as soon as they have been given, and so we have for all practical purposes, although in reality half a second has elapsed while the sound has been coming across the field. The time taken by sound in traveling is more apparent when the volume is sufficient to carry it a long distance. The sound of an explosion of a large quantity of dynamite and ammunition in Jersey City was not heard in Philadelphia, ninety miles away, for over seven minutes alter it occurred.

Cliff Dwellings, Walpi, Arizona.

Photo by Brown Bros. HOMES OF THE LONG-AGO.

Famous reproduction of the Cliff-dwellers' Ruins, near Colorado Springs, Col. The cliff-dwellers of early America built their habitations in the canyons of the Colorado and Rio Grande, where the action of the elements had worn away a layer of soft rock, leaving layers of hard rock above and below as roof and floor for the dwelling.