664 THE POPULAR SCIENCE MONTHLY. 



ELECTKICITY AND AGRICULTURE. 



By Dr. PAGET HIGGS. 



ML. GRANDE ATI, Professor in the School of Forestry, of 

 France, was the first to point out definitely the influence of 

 atmospheric electricity on the nutrition of vegetation. 



His labors are described in the "Annales de Chimie et de Phy- 

 sique," for February, 1879, and he there gives the results of experi- 

 ments carried out in 1876-78. 



These experiments are little known, but are of the highest impor- 

 tance to agriculture. As they bear upon similar experiments under- 

 taken by the writer, a resume is merited. M. Grandeau was led, from 

 the common observation that the underwood in a dense forest disap- 

 pears, to consider the influence of trees on the vegetation beneath 

 them. Studying the causes generally assigned in explanation of this 

 natural phenomenon, such as diminution of light, and the influence of 

 the green light reflected by the trees, these appeared to him insuffi- 

 cient, and he concluded that the loss of electricity, due to the trees 

 acting as an electrical screen, was the cause of the retarded growth 

 a theory that his experiments, as well as those of M. Mascart, ulti- 

 mately confirmed. 



The experiments consisted in placing plants under similar condi- 

 tions of soil, light, and water, but covering one plant with a cage of 

 iron-wire netting of very large mesh, the netting acting as a faradic 

 cage, or somewhat as a lightning-conductor ; the wires of the netting 

 were one fiftieth of an inch in diameter, and the mesh six inches by 

 four. Illustrative of the effect of this arrangement, the case may be 

 cited of two tobacco-plants, otherwise under similar conditions : 



Without Cage. Under Cage 



Total height 1"05 metre 0-69 metre 



Number of leaves 14 10 



Weight of fresh leaves 107 grammes 70 grammes 



Chemical analysis showed defective nutrition in the plant placed 

 under the cage, and withdrawn from electric influence. These ex- 

 periments were greatly extended, and trials were made as to the rela- 

 tion of electrical effect and nitrification of the soil, and the assimila- 

 tion of the ammonia of the atmosphere by plants. ,The results are 

 summed up by M. Grandeau as follows : 



" That trees withdraw, for their own profit, electricity from the 

 atmosphere, and insulate, as completely as a metallic cage, the plants 

 they cover. Insulation produced by a high tree can extend to the 

 extreme limits of its foliage. A plant withdrawn from the influence 



