740 



Popular Science Monthly 



the base, and two thousand and one hun- 

 dred feet long on the crest. The total cost 

 of the reservoir was about $5,000,000. 



A large water power plant has been con- 

 structed below the dam, to convert the 

 energy of the water as it is released from 

 the reservoir into electric power. As this 

 plant will in a few hours use up all the 

 water available for an entire day, a bal- 

 ancing or equalizing reservoir has been 

 built a short distance below the power 

 house to receive the water discharged from 

 the turbines and deliver it uniformly 

 throughout the twenty-four hours to the 

 stream below. 



The other ten 

 reservoirs on the 

 Ruhr Basin were 

 built between 

 1894 and 1912, 

 and vary in ca- 

 pacity from six- 

 teen to six hun- 

 dred and sixty 

 million cubic feet. 

 The dams are all 

 of rubble mason- 

 ry, arched up- 

 stream like the 

 Mohne Dam, and 

 vary in height 

 from sixty-four to 

 one hundred and 

 thirty-three feet. 



A project much 

 like the original Ruhr Association has re- 

 cently been proposed on the Naugatuck 

 River in Connecticut. Twenty-five cor- 

 porations with manufacturing plants along 

 this stream have agreed to cooperate in 

 the construction of three storage reser- 

 voirs with a combined capacity of 1,736,- 

 000,000 cubic feet at a cost of several 

 million dollars. The purpose of these re- 

 servoirs is to increase the low-water flow 

 in order to overcome the present shortage 

 of water for industrial purposes. 



The Beaver River Valley in western Penn- 

 sylvania presents ideal conditions for the 

 formation of a water users' association 

 modeled after that on the Ruhr River. 

 The low-water flow is entirely inadequate 

 to supply the thickly populated manufac- 

 turing district bordering the river. The 

 State Water Supply Commission in 1912 

 showed that a storage reservoir impound- 

 ing about eight billion cubic feet could 

 be built at a cost of about $1,600,000. 



Underwood and Underwood, N 



Looking into the little inclined mirror in front of him 

 the soldier sees the image of the rifle sights and 

 the view beyond, thrown from the mirror above 



Combining the Periscope with the 

 Military Rifle 



PERISCOPE, an instrument for seeing 

 over intervening objects" — so the dic- 

 tionary says. 



About three hundred ingenious and hope- 

 ful inventors have gone to the Patent 

 Office and then to various military head- 

 quarters with different designs of periscope- 

 sighted rifles since the war began. Most 

 of these schemes were more ingenious than 

 practical ; few of them had enough original- 

 ity to be worth much. 



The rifle attachment here illustrated is 

 one of the most 

 workmanlike and 

 practical applica- 

 tions of the idea 

 of so rigging a rifle 

 with a pair of 

 mirrors that one 

 can "lay" it ac- 

 curately on the 

 other fellow while 

 remaining snugly 

 below the trench 

 level and exposing 

 only the rifle. 



The primary 

 principle of all 

 such arrange- 

 ments is that if 

 you place a mirror 

 on a line with the 

 sights of the rifle 

 and arrange it at the proper angle, and 

 have another mirror a sufficient distance be- 

 low, the second mirror picks up from the first 

 one above the image of the rifle sights 

 and reveals the spot where the enemy is 

 supposed to be. 



Gazing at the little incHned mirror in 

 front of him, the soldier sees the reflection 

 of the rifle sights and the view beyond 

 the rifle, sent down by the mirror placed 

 at the top end of the tube. The rifle is 

 aligned and held against the kick of firing 

 by the detachable piece fastened to the 

 rifle stock, while it is fired in the normal 

 way. The soldier is therefore able to take 

 accurate aim without exposing himself above 

 the trench parapet. Tommy Atkins aided 

 by Mother Necessity, evolved a dozen difl^er- 

 ent modifications of the periscope idea, from 

 two bits of pocket mirror, and some sticks. 

 Try it yourself with a piece of cut-out stove 

 pipe and two mirrors placed at proper 

 angles at top and bottom. 



