Page:Popular Science Monthly Volume 22.djvu/69

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59
SCIENCE IN RELATION TO THE ARTS.

of electricity. Taking the loss of effect in all cases as 50 per cent, electric transmission presents the advantage that an insulated wire does the work of a pipe capable of withstanding high internal pressure, which latter must be more costly to put down and to maintain. A second metallic conductor is required, however, to complete the electrical circuit, as the conducting power of the earth alone is found unreliable for passing quantity currents, owing to the effects of polarization; but, as this second conductor need not be insulated, water or gas pipes, railway metals, or fencing-wire, may be called into requisition for the purpose. The small space occupied by the electro-motor, its high working speed, and the absence of waste products, render it specially available for the general distribution of power to cranes and light machinery of every description. A loss of effect of 50 per cent does not stand in the way of such applications, for it must be remembered that a powerful central engine of best construction produces motive-power with a consumption of two pounds of coal per horsepower per hour, whereas small engines distributed over a district would consume not less than five; we thus see that there is an advantage in favor of electric transmission as regards fuel, independently of the saving of labor and other collateral benefits.

To agriculture, electric transmission of power seems well adapted for effecting the various operations of the farm and fields from one center. Having worked such a system myself in combination with electric lighting and horticulture for upward of two years, I can speak with confidence of its economy, and of the facility with which the work is accomplished in charge of untrained persons.

As regards the effect of the electric light upon vegetation there is little to add to what was stated in my paper read before Section A last year, and ordered to be printed with the report, except that, in experimenting upon wheat, barley, oats, and other cereals sown in the open air, there was a marked difference between the growth of the plants influenced and those uninfluenced by the electric light. This was not very apparent till toward the end of February, when, with the first appearance of mild weather, the plants, under the influence of an electric lamp of 4,000 candle-power placed about five metres above the surface, developed with extreme rapidity, so that by the end of May they stood above four feet high, with the ears in full bloom, when those not under its influence were under two feet in height, and showed no sign of the ear.

In the electric railway first constructed by Dr. Werner Siemens, at Berlin, in 1879, electric energy was transmitted to the moving carriage or train of carriages through the two rails upon which it moved, these being sufficiently insulated from each other by being placed upon well creosoted cross-sleepers. At the Paris Electrical Exhibition, the current was conveyed through two separate conductors making sliding or rolling contact with the carriage, whereas in the electric railway now