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Influence of Electric Light upon Vegetation. [Mar. 4 y 



sixteen shillings. If, however, an engine can be found doing other 

 descriptions of work during the day time, the cost of steam-power 

 and attendance for the night-work only would be considerably 

 reduced. In the calculation just given, I have assumed the employ- 

 ment of fuel for the production of mechanical energy, whereas the 

 question will assume a totally different aspect if natural sources of 

 power, such as waterfalls, can be made available within the reasonable 

 distance of half-a-mile. The expenditure for energy will, in that case, 

 be almost entirely saved, and that of attendance be greatly diminished,, 

 and under such circumstances it seems probable that electro-horti- 

 culture may be carried out with considerable advantage. 



The experiments furnish proof that the management of the elec- 

 trical apparatus presents no particular difficulty, as the gas-engine, 

 dynamo-machine ; and regulator have been under the sole management 

 of my head gardener, Mr. D. Buchanan, and his son an assistant 

 gardener. The regulator requires no attention beyond the replace- 

 ment of carbons every four or five hours, which period may easily 

 be increased to twelve hours, by a slight modification of the lamp. 



Conclusions. 



The experiments seem to lead to the following conclusions : — 



1. That electric light is efficacious in producing chlorophyl, in the 

 leaves of plants, and in promoting growth. 



2. That an electric centre of light, equal to 1,400 candles, placed at 

 a distance of 2 metres from growing plants, appeared to be equal in 

 effect to average daylight at this season of the year, but that more 

 economical effects can be attained by more powerful light centres. 



3. That the carbonic acid and nitrogenous compounds generated in 

 diminutive quantities in the electric arc, produce no sensible dele- 

 terious effects upon plants enclosed in the same space. 



4. That plants do not appear to require a period of rest during the 

 twenty-four hours of the day, but make increased and vigorous pro- 

 gress if subjected during daytime to sunlight and during the night to 

 electric light. 



5. That the radiation of heat from powerful electric arcs can be 

 made available to counteract the effect of night frost, and is likely to 

 promote the setting and ripening of fruit in the open air. 



6. That while under the influence of electric light, plants can 

 sustain increased stove heat without collapsing, a circumstance favour- 

 able to forcing by electric light. 



7. That the expense of electro-horticulture depends mainly upon 

 the cost of mechanical energy, and is very moderate where natural 

 sources of such energy, such as waterfalls, can be made available. 



Since writing the above my attention has been drawn to an article 

 in " Nature," 29th January, 1880, giving interesting observations by 



