46 



ROYAL SOCIETY OF CANADA 



the head, and with the loss of a very small quantity of water. The valve 

 is a gun-metal disc J inch in thickness and about 24 inches in diameter. 

 This is let into a depression in the side of the tank of the same dimensions, 

 so that the surface of the disc is flush with the inside surface of the side. 

 The surface of the tank is provided with a gun-metal face, on which the 

 disc beai-s. forming a water-tight bearing. The disc can be rotated by 

 means of a spindle through its centre, and passing through a gland in 

 the side of the tank and connected with a lever on the outside. 



There is a large circular hole in the side of the tank 7^^ inches in 

 diameter, and a cap is provided to screw into it, making it practically 



Experimental Tank. Fig. I. 



water tight when it is desired to change the orifice, Tn the valve there is 

 also a hole of 3 inches diameter. This is screwed and a bush of gun-metal 

 provided to screw into it. The faces of this bush, when screwed home, 

 are exactly flush with those of the valve. The bush can be withdrawn 

 by means of a special ke}^ which projects through a gland in the cap 

 aforementioned. It is into this bush that the orifice plates are fitted. 

 The bush has a 2-inch diameter hole through the centre, \yith a rim y^ of 

 an inch less on the inside. The orifice plate is the same size as this hole 

 and about -16 inch thick ; it is turned to fit the rim in the bush, so that 



