k 



ON SOME APrLICATIONS OF ELECTRIC ENEKGY. 475 



The arrangement consists of a higli-pressnre steam-engine of six 

 horse-power nominal, supplied by Messrs. Tangye Brothers, which gives 

 motion to two dynamo-machines (Siemens D), connected separately to 

 two electric lamps, each capable of emitting a light of about 4,000 candle- 

 power. One of these lamps was placed inside a glass house of 2,318 

 cubic feet capacity, and the other was suspended at a height of twelve to 

 fourteen feet, over some sunk greenhouses. The waste steam of the 

 engine was condensed in a heater, whence the greenhouses take their 

 circulating supply of hot water, thus saving the fuel that would other- 

 wise be required to heat the stoves. 



The experiments were commenced on October 28, 1880, and were 

 continued till May 7, 1881. The general plan of operation consisted in 

 lighting the electric lights at first at six o'clock, and during the short 

 days at five o'clock every evening except Sunday, continuing their action 

 until dawn. 



The outside Hght was protected by a clear glass lantern, whilst the 

 light inside the house was left naked in the earlier experiments, one of 

 my objects being to ascertain the relative eSect of the light under these 

 two conditions. The inside light was placed at one side over the entrance 

 into the house, in front of a metallic reflector to save the rays that would 

 otherwise be lost to the plants within the house. 



The house was planted in the first place with peas, French beans, 

 wheat, barley and oats, as well as with cauliflowers, strawberries, rasp- 

 berries, peaches, tomatoes, vines, and a variety of flowering plants 

 including roses, rhododendrons and azaleas, all these plants being of a 

 comparatively hardy character ; the temperature in this house was main- 

 tained as nearly as possible at 60° Fahr. 



The early effects observed wei-e anything but satisfactory. While 

 under the influence of the light suspended in the open air, over the sunk 

 houses, the beneficial effects due to the electric light, observed during the 

 previous winter, repeated themselves, the plants in the house with the 

 naked electric light soon manifested a withered appearance. Was this 

 result the effect of the naked light, or was it the effect of the chemical 

 products — nitrogenous compounds and carbonic acid — which are produced 

 in the electric arc ? 



Proceeding on the first-named assumption, and with a view of soften- 

 ing the ray of the electric arc, small jets of steam were introduced into 

 the house through tubes, drawing in atmospheric air with the steam, 

 and producing the effect of clouds interposing themselves in an irregular 

 fashion between the light and the plants. This treatment was decidedly 

 beneficial to the plants, although care had to be taken not to increase the 

 amount of moisture thus introduced beyond certain limits. As regards 

 the chemical products — carbonic acid and nitrogenous compounds — it 

 was thought that these would prove rather beneficial than otherwise 

 in furnishing the very ingredients upon which plant-life depends, and 

 further that the constant supply of pure carbonic acid resulting from the 

 gradual combustion of the carbon electrodes, might render a diminution 

 in the supply of fresh air possible, and thus lead to economy of fuel. 

 The plants did not, however, take kindly to these innovations in their 

 mode of life, and it was found necessary to put a lantern of clear glass 

 round the light, for the double purpose of discharging the chemical 

 products of the arc, and of interposing an effectual screen between the 

 arc and the plants under its influence. 



