NOTE I.

ON THE LIGHTNING CONDUCTOR AT BEREHAVEN.[40]

It is satisfactory to know that the lightning conductor referred to in my lecture as attached to the lighthouse at Berehaven has been put in good order under the best scientific guidance. The following interesting letter from Professor Tyndall, which appeared in theTimes, August 31, 1887, gives the history of the matter very clearly, and fully bears out the views put forward in my lecture:“Your recent remarks on thunderstorms and their effects induce me to submit to you the following facts and considerations. Some years ago a rock lighthouse on the coast of Ireland was struck and damaged by lightning. An engineer was sent down to report on the occurrence; and, as I then held the honorable and responsible post of scientific adviser to the Trinity House and Board of Trade, the report was submitted to me. The lightning conductor had been carried down the lighthouse tower, its lower extremity being carefully embedded in a stone perforated to receive it. If the object had been to invite the lightning to strike the tower, a better arrangement could hardly have been adopted.“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, constitutesa 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.”

“Your recent remarks on thunderstorms and their effects induce me to submit to you the following facts and considerations. Some years ago a rock lighthouse on the coast of Ireland was struck and damaged by lightning. An engineer was sent down to report on the occurrence; and, as I then held the honorable and responsible post of scientific adviser to the Trinity House and Board of Trade, the report was submitted to me. The lightning conductor had been carried down the lighthouse tower, its lower extremity being carefully embedded in a stone perforated to receive it. If the object had been to invite the lightning to strike the tower, a better arrangement could hardly have been adopted.

“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, constitutesa 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.”

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 theElectrician, June and July, 1888, in which some new views are put forward respecting lightning conductors, that seem deserving of careful consideration.

Since the above was in print, two lectures given before the Society of Arts by Professor Oliver Lodge, F. R. S., have appeared in theElectrician, 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.[19]See Report of Lightning Rod Conference,p.119.[20]Loco citato.[21]Sir William Snow Harris,loco citato,p.274.[22]Id.,p.275.[23]The Thunderstorm, by Charles Tomlinson, F.R.S., Third Edition,p.172.[24]See for these facts, Anderson, Lightning Conductors,p.197; Tomlinson, The Thunderstorm,pp.167-9; Harris,loco citato,pp.273-4.[25]See Anderson, Lightning Conductors,pp.170-5.[26]The Thunderstorm,pp.158-9. See also an account of four persons who were struck on the Matterhorn, in July, 1869, all of whom were hurt, and none killed: Whymper’s Scrambles Among the Alps,pp.414, 415.[27]See Philosophical Transactions of the Royal Society, 1773,p.42, and 1778, part i.,p.232; Anderson’s Lightning Conductors,pp.40-2; Lighting Rod Conference,pp.76-9.[28]See A Lecture on Thunderstorms, by Professor Tait of Edinburgh, published in Nature,vol.xxii.,p.365.[29]Report of the Lightning Rod Conference,p.4.[30]The dimensions here set forth are greater in some respects than those “recommended as a minimum” in the report of the Lightning Rod Conference, page 6. But it will be observed by those who consult the report that the minimum recommended is just the size which, in the preceding paragraph of the report, is said to have been actually melted by a flash of lightning; and, therefore, it seems not to be a very safe minimum. It will be also seen that there is some confusion in the figures given, and that they contradict one another. For the dimensions of iron rods, see the instructions adopted by the Academy of Science, Paris, May 20, 1875; Lightning Rod Conference,pp.67-8.[31]See letter ofMr.R. S. Newall, F. R. S., in theTimes, May 30, 1879.[32]See Nature, June 12, 1879,vol.xx.,p.146.[33]See letter ofMr.Tomes in Nature,vol.xx.,p.145; also Lightning Rod Conference,pp.210-15.[34]See Anderson, Lightning Conductors,pp.208-10.[35]See Lightning Rod Conference,pp.208-10; see also the note at the end of this Lecture,p.52.[36]Lecture on Thunderstorms, Nature,vol.xxii.,pp.365, 437. See, also, a very interesting paper by the late Professor J. Clerk Maxwell, read before the British Association at Glasgow in 1876, and reprinted in the report of the Lightning Rod Conference,pp.109, 110.[37]Nature,vol.xxxi.,p.459.[38]See further information on this interesting subject in the Report of the Lightning Rod Conference,pp.233-5.[39]See “Die Theorie, die Anlage, und die Prüfung der Blitzableiter,” von Doctor W. Holtz, Griefswald, 1878.[40]Seepage 44.

[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.

[19]See Report of Lightning Rod Conference,p.119.

[20]Loco citato.

[21]Sir William Snow Harris,loco citato,p.274.

[22]Id.,p.275.

[23]The Thunderstorm, by Charles Tomlinson, F.R.S., Third Edition,p.172.

[24]See for these facts, Anderson, Lightning Conductors,p.197; Tomlinson, The Thunderstorm,pp.167-9; Harris,loco citato,pp.273-4.

[25]See Anderson, Lightning Conductors,pp.170-5.

[26]The Thunderstorm,pp.158-9. See also an account of four persons who were struck on the Matterhorn, in July, 1869, all of whom were hurt, and none killed: Whymper’s Scrambles Among the Alps,pp.414, 415.

[27]See Philosophical Transactions of the Royal Society, 1773,p.42, and 1778, part i.,p.232; Anderson’s Lightning Conductors,pp.40-2; Lighting Rod Conference,pp.76-9.

[28]See A Lecture on Thunderstorms, by Professor Tait of Edinburgh, published in Nature,vol.xxii.,p.365.

[29]Report of the Lightning Rod Conference,p.4.

[30]The dimensions here set forth are greater in some respects than those “recommended as a minimum” in the report of the Lightning Rod Conference, page 6. But it will be observed by those who consult the report that the minimum recommended is just the size which, in the preceding paragraph of the report, is said to have been actually melted by a flash of lightning; and, therefore, it seems not to be a very safe minimum. It will be also seen that there is some confusion in the figures given, and that they contradict one another. For the dimensions of iron rods, see the instructions adopted by the Academy of Science, Paris, May 20, 1875; Lightning Rod Conference,pp.67-8.

[31]See letter ofMr.R. S. Newall, F. R. S., in theTimes, May 30, 1879.

[32]See Nature, June 12, 1879,vol.xx.,p.146.

[33]See letter ofMr.Tomes in Nature,vol.xx.,p.145; also Lightning Rod Conference,pp.210-15.

[34]See Anderson, Lightning Conductors,pp.208-10.

[35]See Lightning Rod Conference,pp.208-10; see also the note at the end of this Lecture,p.52.

[36]Lecture on Thunderstorms, Nature,vol.xxii.,pp.365, 437. See, also, a very interesting paper by the late Professor J. Clerk Maxwell, read before the British Association at Glasgow in 1876, and reprinted in the report of the Lightning Rod Conference,pp.109, 110.

[37]Nature,vol.xxxi.,p.459.

[38]See further information on this interesting subject in the Report of the Lightning Rod Conference,pp.233-5.

[39]See “Die Theorie, die Anlage, und die Prüfung der Blitzableiter,” von Doctor W. Holtz, Griefswald, 1878.

[40]Seepage 44.

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