216 



Dr. C. W. Siemens. 



[Mar. 4, 



inferior temperature in the other, and npon the early vegetables un- 

 provided with covering. 



Some weeks must elapse before any absolute results can be given, 

 but growth is evidently promoted under all these various circum- 

 stances. In order to test this clearly, a portion of the plants both 

 under glass and in the open air are shaded from the electric light 

 without removing them from their position of equal temperature,, 

 and exposed to solar light during daytime. The effect upon the 

 flowering plants is very striking, electric light being apparently 

 more efficacious to bring them on than daylight. Although the 

 amount of heat given off from the electric arc is not great compared 

 with a gas flame (giving off its products of combustion), yet the ray& 

 of intense heat of the arc counteract that loss of heat by radiation 

 from the leaves into space, which during a clear night causes hoar 

 frost. For this reason I expect that electric light may be usefully 

 employed in front of fruit walls, in orchards and in kitchen gardens,, 

 to save the fruit-bud at the time of setting ; and in this application 

 electric light will probably be found a useful agent not only to pro- 

 mote rapid growth, but to insure a better yield of fruit. Experience 

 alone can determine absolutely the effect of electric light upon the 

 ripening of delicate fruit, but considering its evident power to form 

 chlorophyl, there seems no reason to suppose that its action would not 

 also in this case resemble that of the sun, and that saccharine matter, 

 and more especially the aromatic constituents, would be produced. In 

 this country solar light is too often found insufficient to ripen the 

 fruit or even the wood of fruit trees during the short summer months ; 

 and I believe that electric light will be found a most useful auxiliary 

 to solar light to effect the production of ripe and aromatic fruit both 

 under glass and in the open air. 



Estimated Cost of Electro -Horticulture. 



A very important question is that of the cost of electro-horticulture. 

 This will depend in a great measure upon the cost of the fuel or other 

 source of energy, and upon the scale of application. To work only 

 one electric lamp by means of a small steam or gas engine is expensive 

 both in fuel and in cost of attendance. If steam-power has to be re- 

 sorted to, an engine of sufficient size should be employed to give 

 economical results per horse-power of energy produced, and the electric 

 arc should be of sufficient brilliancy to give a good effect for the power 

 expended. Experience in electric illumination has established a form 

 and size of machine, both convenient and suitable for the attainment 

 of economical results, viz., the medium dynamo-electric machine, 

 which, if applied to a suitable regulator, produces fully 6,000 candle- 

 power of diffused light with an expenditure of 4 horse-power. 



The experiments before given show that the most effective height 



