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. 



429 

 the 



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 



