/ TURBINES 229 



stock connection is at the top or the side, the gate mechanism may 

 be exposed, which is not the case if the penstock is connected at 

 the end. In the latter case, however, the hydraulic conditions 

 are better. In general, the plate steel cylindrical type of casing is 

 more or less out of date. Fig. 122 shows a unit of the end intake 

 type which has given high efficiency in tests made on the com- 

 pleted installation. 



FIG. 120. Double-runner Horizontal Turbines with Cast-iron Spiral Case and 

 Double Discharge Tube. Hydraulic Power Company, Niagara Falls. 

 (Built by I. P. Morris Company.) 



Vertical Turbines. Multi-runner vertical turbines are open to 

 the same objections as horizontal units in that the gate mechanism 

 is submerged and the machine more complicated. The best prac- 

 tice of to-day, therefore, adheres to the single vertical turbine. 

 The casing is of volute or spiral form and for low heads is usually 

 molded in the concrete foundations of the power-house (Fig. 123). 

 For higher heads it is made of cast-iron, cast-steel or riveted-steel 

 plate, as conditions may require. Sometimes the metal casing is 

 imbedded in concrete under the floor which supports the generator 



