5/A 1 \\-ll.UAM AY /:.]//.. Y\, F.R.S. 197. 



specific purposes, except to a very small extent. The application 

 of natural forces has, indeed, yielded in recent times to what may 

 be called the artificial employment of coal ; the ancient water- 

 wind has in many cases gone to ruin, windmills no longer crowd 

 tin- elevated ground near our towns and villages, and the steam 

 funnel, with its flag of suffocating smoke, has superseded, to a 

 extent, the more graceful but less certain sail for the pro- 

 pulsion of our vessels. This change has been the natural conse- 

 quence of the abundant supply of coal which we now enjoy ; but 

 tli is supply, as I have endeavoured to show, is not without limit, 

 and the time will come when man will have to revert to those 

 natural forces upon which he has for the present turned his 

 back. 



It would, however, be wrong to suppose that a resumption of 

 the use of natural forces would throw us back to the time of the 

 windmill and the primitive water-wheel which used to give motion 

 to isolated establishments. We shall have learned to store, to 

 transport, and to utilise these forces in a manner adapted to our 

 superior requirements ; and who knows whether the time may not 

 come when our descendants in the third or fourth generation will 

 look back upon the indiscriminate users of coal with something 

 like the same feeling that we look upon the users of flint and 

 bronze implements. Indeed, without waiting for the extinction 

 of our coal-fields, it appears to me not improbable that natural 

 forces will be resorted to simply on account of their comparative 

 cheapness and convenience of application. 



When little more than a twelvemonth ago I visited the great 

 falls of Niagara, I was particularly struck with the extraordinary 

 amount of force which is lost, as far as the useful purposes of man 

 are concerned. 100,000,000 of tons of water fall there every hour 

 from a vertical height of 150 feet, which represents an aggregate 

 of 16,800,000 horse-power, producing as their effect no other 

 result than to raise the temperature of the water at the foot of 



the fall - = Fahr. In order to reproduce the power of 

 772 5 



10,800,000 horses, or, in other words, to pump back the water 

 from below to above the fall, would require an annual expenditure 

 of not less than 266,000,000 of tons of coal, calculated at an 

 average consumption of 4 Ibs. of coal per horse-power per hour : 



