The next experiment in this country of any note, was one by 

 Mr. B. H. Thwaite, undertaken in the year 1907 at the Royal 

 Botanic Gardens, London. Mr. Thwaite had an arc lamp 

 mounted upon an automatic carrier, installed in one of the green- 

 houses, which constantly, but almost imperceptibly, moved back- 

 wards and forwards along the roof of the whole house. The more 

 powerful rays of the lamp were cut off by a specially contrived 

 water screen, and the light was turned en every day at sunset 

 and kept alight from four to five hours. 



Another greenhouse was kept as a control house, and in both 

 houses chrysanthemums, geraniums and tomatoes were planted. 

 By the end of the first month considerable difference was observed 

 between those plants grown under the light and those away from 

 it, the former grew much more rapidly, and were in those few 

 weeks almost twice the height of the control ones. The foliage 

 was of a much deeper green, showing an increase of chlorophyl, 

 which is one of the most important factors in plant composition, 

 upon which they greatly depend for the manufacture of their most 

 important foods. The tomatoes showed a lanky appearance, 

 although they had ample fcliage possibly the light had been too 

 powerful for the size of the house in which they were grown. 

 Unfortunately this experiment was not completed owing to Mr. 

 Thwaite's illness and subsequent death. 



L Mr. L. H. Bailey, of Cornell University, U.S.A., made a series 

 of most interesting experiments in plant culture by the aid of 

 electric arc light. As the result of his experiments he gave his 

 opinion as follows : " That the general effect of the electric light 

 was to hasten maturity, and the nearer the plants were to the 

 light the greater the acceleration, which was particularly marked 

 in the case of crops like endive, spinach, cress and lettuces " but 

 if too near the light he noticed a tendency to run to seed. 

 Lettuces withm three feet of the light were killed outright if 

 grown at a suitable distance from the lamp he considered the 

 effect of the radiation made the plants more vigorous, though 

 not so vigorous as those grown in sunlight ; but for lettuce growing 

 he was of opinion the electric light would be a source of profit. 

 He also considered that flowers benefited by it. 



One of the market gardeners in Boston has used electric light 

 for many years in the raising of lettuces, and considers it to have 

 an advantageous effect, and to be a source of profit. Amongst 

 other experiments in America those of Mr. F. W. Rane, of West 

 Virginia Experimental College, are of interest. He made use of 

 the ordinary incandescent electric light such as is used for lighting 

 houses. He considered as a result of his experiments : 



1. That the incandescent light has a marked effect on green- 

 house plants. 



2. That the light is beneficial to plants grown for foliage ; 

 lettuces matured earlier, stood more erect and weighed more. 



