232 THE SCIENTIFIC PAPERS OF 



in order to protect the plants from" cold winds. The effects could 

 thus be simultaneously observed upon the melons and cucumbers 

 in the one house, upon the roses, strawberries, etc., at a lower 

 temperature, in the other, and upon the early vegetables unprovided 

 with covering. 



That growth was promoted under all these varying circum- 

 stances, I proved clearly, by shading a portion of the plants both 

 under glass and in the open air from the electric light, without 

 removing them from their position of equal temperature, and 

 exposing them to solar light during day-time. Upon flowering 

 plants the effects are very striking, and the electric light is ap- 

 parently more efficacious to bring them forward than daylight in 

 winter. Although the quantity of heat given off by the electric 

 light is not so great in amount as that from burning gas, yet the 

 heat rays from the arc counteract that loss of heat from the leaves 

 by radiation into space, which causes hoar frost on a clear night. 

 An experiment made during a night of hoar frost clearly proved 

 that although the temperature on the ground did not differ mate- 

 rially within the range of the electric light and beyond it, the 

 radiant effect of the light was such as to prevent frost entirely 

 within its range. For this reason I anticipate the useful applica- 

 tion of electric light in front of fruit walls, in orchards, and in 

 kitchen gardens, to save the fruit bud at the time of setting. 



Considering the evident power of the electric light to form 

 chlorophyll, there seemed reason to suppose that its action would 

 also in the case of ripening fruit resemble that of the sun, and 

 that saccharine matter, and more especially the aromatic constitu- 

 ents, would be produced. To test this opinion practically, several 

 plants of early strawberries in pots were placed, as in the last 

 experiment, in two groups, the one being subjected to daylight 

 only, and the other to solar light during the day and to electric 

 light at night. Both groups were placed under glass, at tempera- 

 tures varying from 65 to 70 Fahr., those that received daylight 

 only being shielded from the effect of the electric light. 



At the commencement of the experiment the strawberry plants 

 were partly setting fruit, and partly in bloom. After a week the 

 fruit on the plants exposed to electric light had swelled very much 

 more than that on the others, some of the berries showing signs of 

 ripening. The experiment was interrupted for two nights at this 



