814 The Outline of Science 



direct or after doing further duty in another turbine. A turbine 

 is so well balanced and revolves, a thousand times or more per 

 minute, so smoothly, that a coin stood on edge on the casing is 

 not upset. 



7 



Importance of Water-Power 



The scale on which the world's water-powers have been 

 explored and developed during the last ten years is one of the 

 most significant engineering features of the decade. Three times 

 as much water-power is used now as was used ten years ago. 

 The advance has naturally been most rapid in those countries 

 which have depended in the past for their power largely on 

 imported fuel where "white coal" may be substituted for black. 

 Thus, France has added 850,000 h.p. to the 750,000 h.p. of 1915; 

 Switzerland now has some 1,500,000 h.p. as compared with 850,- 

 000 h.p. in 1914; the output in Spain is 900,000 h.p. as against 

 150,000 h.p. before the war, and that country is engaged on a 

 scheme for developing a further 2,000,000 h.p. The same kind 

 of story may be told of Canada, the United States, Italy, Japan, 

 Norway, Sweden, and India; where also the water turbine is 

 rapidly altering industrial conditions, despite the liberal coal 

 deposits in some of those countries. 



The world's total potential water-power has been calculated 

 at 200 million h.p. Estimates must be accepted with reserve, as 

 the surveys have necessarily been very incomplete in the almost 

 unexplored regions where ultimately some of the greatest de- 

 velopments may be expected. So far only 25,000,000 h.p. of 

 this energy has been turned to account. Even at this stage, 

 however, the economies resulting from harnessing water-power 

 are apparent. In the best steam plant of large size 9 tons of 

 coal must be burned to give one horse-power continuously for a 

 year. Therefore 225,000,000 tons of coal, or approximately the 



