442 POPULAR LECTURES AND ADDRESSES. 



there is so little of it left and the coal-mines from 

 which that little is to be excavated are so distant 

 and deep and hot that its price to the consumer is 

 greatly higher than at present, it is most probable 

 that windmills or wind-motors in some form will 

 again be in the ascendant, and that wind will do 

 man's mechanical work on land at least in 

 proportion comparable to its present doing of 

 work at sea. 



Even now it is not utterly chimerical to think of 

 wind superseding coal in some places for a very 

 important part of its present duty that of giving 

 light. Indeed, now that we have dynamos and 

 Faure's accumulator, the little want to let the 

 thing be done is cheap windmills. A Faure cell 

 containing twenty kilogrammes of lead and 

 minium charged and employed to excite incandes- 

 cent vacuum-lamps has a light-giving capacity of 

 sixty-candle hours (I have found considerably 

 more in experiments made by myself ; but I take 

 sixty as a safe estimate). The charging may be 

 clone uninjuriously, and with good dynamical 

 economy, in any time from six hours to twelve or 



