446 POPULAR LECTURES AND 



be afraid that the scene will be marred by forest :> 

 of iron columns taking the place of natural trees, 

 and gigantic tanks overshadowing the fields and 

 blackening the horizon. 



To use rain-power economically on any consider- 

 able scale we must look to the natural drainage of 

 hill country, and take the water where we find it 

 either actually falling or stored up and ready to 

 fall when a short artificial channel or pipe can be 

 provided for it at moderate cost. The expense of 

 aqueducts, or of underground water-pipes, to carry 

 water to any great distance any distance of more 

 than a few miles or a few hundred yards is much 

 too great for economy when the yield to be pro- 

 vided for is power ; and such works can only be 

 undertaken when the water itself v$> what is wanted. 

 Incidentally, in connection with the water supply 

 of towns, some part of the energy due to the head 

 at which it is supplied may be used for power. 

 There arc, however, but few cases (I know of none 

 except Greenock) in which the energy to spare 

 over and above that devoted to bringing the water 

 to where it is wanted, and causing it to flow fast 



