.S7A' //7/./././.1/ .s/A-.l/A.V.s, /.-.A'..V. 199 



armature or keeper of cylindrical form surrounded by insulated 

 \viivs, laid longitudinally upon the cylinder, and revolving with it 

 in the mau-netic field due to the polar surfaces of electro-magnets, 

 the coils of which are excited by the very current set up through 

 rotation in the wire upon the armature. 



Thus an accumulative principle of action and reaction is 

 inaugurated not altogether dissimilar in principle to the accumu- 

 lat ive action already described to you in reference to the regenera- 

 tive gas furnace, and as in the gas furnace temperatures can be 

 produced limited only by the point of dissociation of combustible 

 matter, so the intensity of electrical action producible in the 

 dynamo-electric machine is limited only by the point of ultimate 

 magnetisation of which iron is capable. As a matter of fact and 

 experiment, a dynamo-electric machine such as is actually 

 employed at the .Lizard Lighthouse, weighing altogether 3 cwts. 

 3 qrs., is capable of converting 3*3 horse-power into electrical 

 energy, which energy is employed for the production of an electric 

 light equal to 4138 candle-power. The smaller machine, which I 

 have placed before you, weighs only 2 cwts. 2 qrs., converts 2 

 horse-power into electrical energy, which energy may be employed 

 for the production of an electric light equal to 1250 candles, or 

 for producing mechanical force capable of being utilised at a 

 distance for giving motion to machinery, for pumping water, or 

 any other useful purpose. Experiments have shown that the 

 amount of mechanical force that may thus be recovered is equal, 

 or nearly equal, to one-half the force expended in the original 

 production of the current. The diagrams placed upon the wall 

 may serve to give you a better idea of the construction of these 

 machines. 



Let us suppose that at some central station 100 horse-power of 

 steam or water power was employed to give motion to several 

 dynamo-electric machines of the dimensions found most convenient 

 in practice, and that by means of metallic conductors of suitable 

 dimensions the electric current produced at the central station was 

 conducted to a number of halls or factories requiring to be lighted, 

 or to utilise mechanical power. If illumination were the only 

 object in view, the total amount of light that could be thus pro- 

 duced would be equal to 125,000 candle-power. This would be 

 equivalent to 0250 Argand burners, each of 20 candle-power, at a 



