Page:Popular Science Monthly Volume 92.djvu/445

 Fopuhir Science Monthly

��interfere with the great quantity produc- tion for which our cars are famous. In handling this work, makes use is made of an air-turbine to revolve the shaft by means of a jet of compressed air impinging upon the surfaces of the vanes of an impeller, mounted directly on the shaft. One of the unusual features of this method is that the method of rotation does not affect the actual or apparent condition of balance of the shaft which is being tested.

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��An Antique Chinese Water-Wheel Ir- rigates a Modern Colorado Orchard

A COLORADO apple-grower irrigates his orchard with a water-wheel of the antique Chinese pattern. This primitive de\'ice supplies his fruit trees with ample moisture at a cost of only eighty-eight cents an acre, while his neighbors, who purchase water from an aggressively modern irrigation ditch pay four dollars an acre.

Water from a small dam furnishes the power which drives the water-wheel. The wheel is provided with buckets, which carry the water to the top, where it is emptied into the box-troughs, shown in the ac- companying illustration. From the troughs, the water is distributed, as needed, to various parts of the orchard.

��A Corrugated Hull Increases Speed of a Ship

THE fact that corrugations in a ship's hull lessen its resistance to the water was discovered by mere accident. A. H. Haver, an English naval architect, was making various experiments in a Caws pendulum tank. This pendulum tank is simply a large tank of water over which a pendulum is suspended. To the bob of the pendulum a model of a ship is at- tached so that the swing of the pendulum draws the model horizontally through the water. The arc of the swing measures the resistance of the model to the water.

An experiment was made with a model having plain sides, and a certain result was obtained. Then corrugations were made in the hull of the model. Instead of reducing the swing of the pendulum on account of the increased wetted area, as was confidently expected, the corrugations increased it.

This proved that the resistance of the ship to the water was decreased in pro- portion as the wetted area was increased. The conclusion naturally followed that a ship with corrugated hull would possess a greater speed than one with a plain hull. It is not possible, however, to conclude that the increase in wetted area is the cause of the greater speed.

���This water-wheel is provided with buckets, which carry the water to the top, where it is emptied into the box-troughs, from which it is distributed about the orchard

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