254 THE SCIENTIFIC PAPERS OF 



The early effects observed were 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 

 tire ? Proceeding on the first-named assumption, and with a 

 view of softening the ray of the electric arc, small jets of steam 

 were introduced into the house through tubes, drawing in atmo- 

 spheric 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, 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 combus- 

 tion 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 dis- 

 charging the chemical products of the arc and of interposing an 

 effectual screen between the arc and the plants under its influence. 

 The effect of interposing a mere thin sheet of clear glass between 

 the plants and the source of electric light was most striking. On 

 placing such a sheet of clear glass so as to intercept the rays of 

 the electric light from a portion only of a plant for instance, a 

 tomato plant it was observed that in the course of a single night 

 the line of demarcation was most distinctly shown upon the 

 leaves. The portion of the plant under the direct influence of the 

 naked electric light, though at a distance from it of 9 feet to 10 

 feet, was distinctly shrivelled, whereas that portion under cover of 

 the clear glass continued to show a healthy appearance, and this 

 line of demarcation was distinctly visible on individual leaves. 

 .Not only the leaves, but the young stems of the plants, soon 



