POWER DEVELOPMENT AT NIAGARA, 613 



down, with arrangements in the form of gates in the masonry wall 

 separating it from the canal, by which water may be admitted to 

 penstocks placed vertically in the slot and supplying the turbine 

 wheels. A penstock, as many of our readers are aware, is a great 

 tube, usually, in these days, of boiler plate, of a diameter running 

 up, it may be, to thirteen feet, conveying water under head into 

 the wheel case in which the turbine revolves. 



In the present instance the penstocks, which are seven and a 

 half feet in diameter, seem very small, considering that they each 

 supply a pair of wheels of five thousand horse power, but that is 

 on account of the enormous pressure under which the wheels 

 work, giving a greater power for a given volume of water than 

 with the smaller heads more commonly used. 



The turbines discharge their waste water into the tunnel above 

 referred to, which is no less than six thousand seven hundred feet 

 long, and which discharges into the chasm below the falls just 

 past the Suspension Bridge. 



The details of this tunnel, which was excavated through three 

 shafts, one in the face of the cliff and two vertical ones, are as fol- 

 lows : Length, six thousand seven hundred feet, and sectional area 

 three hundred and eighty -six square feet throughout, the average 

 height and width being about twenty-one and nineteen feet re- 

 spectively. The cross-section somewhat resembles a horseshoe. 

 The excavation was much larger than the finished inside dimen- 

 sions, on account of the subsequent lining with four courses of 

 brick. The mouth of the tunnel has, besides, a lining on the top 

 and sides of iron. The work has been done most substantially 

 and is built to stay. The tunneling was done through strata of 

 limestone and shale, and harder material was met with than had 

 been expected in the beginning, so that the three million cubic 

 feet of excavation has cut a very important figure in the total 

 cost of the power plant. The tunnel has a grade of 07 per cent 

 (seven feet fall per thousand length), and runs directly under the 

 city of Niagara Falls to the lower river level. 



The work of excavation was carried on on three benches, divid- 

 ing the total height of twenty-six feet about into three equal por- 

 tions. 



The whole undertaking has been so entirely novel in many 

 ways that the engineers in charge have had their resources taxed 

 to the utmost in overcoming the various difficulties that presented 

 themselves during the design and construction of the power house, 

 electrical and hydraulic apparatus, and tunnel. The power-house 

 building is as yet of comparatively small proportions, but is in- 

 tended to be enlarged as the number of dynamos and turbines is 

 increased. It might be thought, and was thought at first by some 

 of the projectors of the scheme, that the great amount of power 



