Page:Popular Science Monthly Volume 25.djvu/705

Rh was established by this threefold distribution amounted altogether to 333,000 square yards of conducting communication. Iron rods were used in preference to copper in this construction on account of the cost which would have been entailed if copper had been employed for so extensive a work, and also because Professor Melsens had satisfied himself that iron has more tenacity and power of cohesion than copper when exposed to the disintegrating strain of powerful discharges of electricity. He devised a very pretty experimental proof of this, in which the discharge of a large battery of Leyden-jars was passed through a fine wire of equal dimensions throughout, but of which one half was composed of copper and the other half of iron. The iron portion was converted into a beaded, but still unbroken, strand by the discharge, but the copper part was scattered into a black impalpable powder. It is scarcely too much to say that the Hôtel de Ville at Brussels at the present day, with its lofty aigrette-defended tower, its forest of points, its net-work of rods, and its widely ramifying earthroots, is, as far as danger from lightning is concerned, one of the best protected buildings in the world. It may safely be affirmed that it is quite as hard for the lightning to get mischievously at this building, as it is for the discharge of the Leyden battery to get at Professor Melsens's birds when they are inclosed in their iron cage. In the heaviest of storms Professor Melsens travels about within the meshes of his system of conductors, to investigate their behavior, with the most perfect sang-froid and confidence. In 1866 Professor Melsens examined with great care the transmitting capacity of his system of conductors at the Hôtel de Ville, and in this final investigation he employed all the various means that are now at the command of science. He used continuous currents, instantaneous discharges, sparks from the electrical machine, from powerful batteries, and from a large Ruhmkorff coil, and with all he found that the conductibility of his system was practically perfect.

One of the grounds upon which Professor Melsens adopts his system of multiple rods is the circumstance that an electrical discharge diffuses itself through all the branches of a multifold conductor in proportion to the resistance which is offered by each part, and that it does not all concentrate itself into the shortest and most open path. He has devised some very ingenious experiments for proving this position, and has been able to show the sixty-thousandth part of a discharge passing by a very narrow and roundabout path, when a broad and direct one was open, and traversed by the larger proportions of the discharge. He brought this part of his subject under the notice of the Academy of Sciences of Belgium in a special note, which was printed in their "Bulletins" in 1875.—Edinburgh Review.