“I gave directions to have the conductor immediately prolonged, and to have added to it a large terminal plate of copper, which was to be completely submerged in the sea. The obvious convenience of a chain as a prolongation of the conductor caused the authorities in Ireland to propose it; but I was obliged to veto the adoption of the chain. The contact of link with link is never perfect. I had, moreover, beside me a portion of a chain cable through which a lightning discharge had passed, the electricity in passing from link to link encountering a resistance sufficient to enable it to partially fuse the chain. The abolition of resistance is absolutely necessary in connecting a lightning conductor with the earth, and this is done by closely embedding in the earth a plate of good conducting material and of large area. The largeness of area makes atonement for the imperfect conductivity of earth. The plate, in fact, constitutes a wide door through which the electricity passes freely into the earth, its disruptive and damaging effects being thereby avoided.
“These truths are elementary, but they are often neglected. I watched with interest some time ago the operation of setting up a lightning conductor on the house of a neighbor of mine in the country. The wire rope which formed part of the conductor was carried down the wall and comfortably laid in the earth below without any terminal plate whatever. I expostulated with the man who did the work, but he obviously thought he knew more about the matter than I did. I am credibly informed that this is a common way of dealing with lightning conductors by ignorant practitioners, and the Bishop of Winchester’s palace at Farnham has been mentioned to me as an edifice ‘protected’ in this fashion. If my informant be correct, the ‘protection’ is a mockery, a delusion, and a snare.”
NOTE II.
BOOKS OF REFERENCE.
As some of my readers may wish to pursue the study of lightning and lightning conductors beyond the limits to which a popular lecture must, of necessity, be confined, I subjoin a list of the books which I think they would be likely to find most useful for the purpose. Among ordinary text-books on physics—Jamin, Cours de Physique, vol. i., pp. 470-494; Mascart, Traité d’Electricité Statique, vol. ii., pp. 555-579; De Larive, A Treatise on Electricity, in three volumes, London, 1853-8, vol. iii., pp. 90-201; Daguin, Traité de Physique, vol. iii., pp. 209-280; Riess, Die Lehre von der Reibungs-Elektricität, vol. ii., pp. 494-564; Müller-Pouillet, Lehrbuch der Physik, Braunschweig, 1881, vol. iii., pp. 210-225; Scott, Elementary Meteorology, chap. x. Of the numerous special treatises and detached papers on the subject, I would recommend Instruction sur les Paratonnerres adopté par l’Académie des Sciences, Part i., 1823, Part ii., 1854, Part iii., 1867, Paris, 1874; Arago, Sur le Tonnerre, Paris, 1837; also his Meteorological Essays, translated by Sabine, London, 1855; Sir William Snow Harris, On the Nature of Thunderstorms, London, 1843; also by the same writer, A Treatise on Frictional Electricity, London, 1867; and various papers on lightning conductors, from 1822 to 1859; Tomlinson, The Thunderstorm, London, 1877; Anderson, Lightning Conductors, London, 1880; Holtz, Ueber die Theorie, die Anlage, und die Prüfung der Blitzableiter, Greifswald, 1878; Weber, Berichte über Blitzschläge in der Provinz Schleswig-Holstein, Kiel, 1880-1; Tait, A Lecture on Thunderstorms, delivered in the City Hall, Glasgow, in 1880, Nature, vol. xxii.; Report of the Lightning Rod Conference, London, 1882. This last-mentioned volume comes to us with very high authority, representing, as it does, the joint labors of several eminent scientific men selected from the following societies: The Meteorological Society, the Royal Institute of British Architects, the Society of Telegraph Engineers and Electricians, the Physical Society.
Since the above was in print, two lectures given before the Society of Arts by Professor Oliver Lodge, F. R. S., have appeared in the Electrician, June and July, 1888, in which some new views are put forward respecting lightning conductors, that seem deserving of careful consideration.
FOOTNOTES:
[17] The Thunderstorm, by Charles Tomlinson, F. R. S., Third Edition, pp. 153-4.
[18] Two Lectures on Atmospheric Electricity and Protection from Lightning, published at the end of his Treatise on Frictional Electricity, p. 273.