Lightning Rod Conference. Various
of the information collected, including replies from America, Belgium, Denmark, Germany, Holland, India, Italy, and Norway, will be found in Appendix H. Full details respecting the practice in France will be found in Appendices F, K, and L, and a notice of Zenger’s Austrian system, on p. (104).
At the meeting, Nov. 20th, 1879, the Secretary was unanimously requested to act as Editor of the Report.
At the meeting, Jan. 22nd, 1880, a letter was received from Mr. R. H. Scott, F.R.S., Secretary to the Meteorological Council, enclosing a report respecting the injury to the “Southern Queen,” it was resolved, “That some of the delegates visit the ship.” The report and a note of the results of the visit will be found in Appendix I page (205).
At the meeting, April 15th, 1880, Prof. D. E. Hughes was unanimously elected member of the Conference.
At the meeting, July 6th, 1880, the Secretary handed in a sketch of a house with various parts of the lightning conductor marked upon it, and obtained from the delegates definite names for each portion, in order that in framing the report there might be no uncertainty as to what was meant by any special term, great confusion in this respect having previously existed.
The terms adopted have been: Conductor.—The whole arrangement for the protection of a building. Point.—The upper termination of the conductor, whether blunt or sharp, single or bifurcated. Upper terminal.—That portion of the conductor which is between the top of the edifice and the point. Joint.—Any connection between any two parts of the conductor. Rod.—The main portion of the conductor, whether it consist of rope, tape, tube or solid rod. Circuit des Faîtes.—A rod running round the eaves of a house, the battlements of a tower, &c. Earth plate.—The termination of the conductor in the ground, the pattern being indicated by special terms.
The accompanying lithograph will, it is hoped, supply all additional necessary particulars.
It is desirable to state that the illustrations in this Report have been prepared by Mr. E. White Wallis, F.M.S., so as to bring out the various features distinctly, and as nearly as possible in true proportion, but without any attempt at artistic finish.
The meetings during the latter part of 1880, and the early part of 1881, were devoted chiefly to the discussion of various questions as bases for the report. Much time was also occupied in perfecting the various appendices, and in compiling an exhaustive index to them.
In May, 1881, Messrs. Preece and Symons, being in Paris, made careful enquiries as to the existing practice in France respecting lightning conductors. Their notes form Appendix K.
At the meeting held on May 27th, 1881, the Secretary was instructed to draw up a draft report, and this having been put in type was sent to all the delegates; carefully considered, revised, and amended at various subsequent meetings, and finally adopted.
INDEX SKETCH OF LIGHTNING CONDUCTOR, ILLUSTRATING THE TERMS EMPLOYED IN THE REPORT.
| TERMS APPLIED TO THE VARIOUS PARTS OF A CONDUCTOR. | |
|---|---|
 |
Crutch |
 |
Strap |
 |
Staple |
 |
Wall Eye |
| A | Point |
| B | Upper Terminal |
| c | Joint |
| D | Rod |
| E | Ridge Rod |
| F | Circuit des faîtes |
| G | Earth Plates |
| G1 | Earth Plates Sanderson |
| G2 | Earth Plates Borrel |
| G3 | Earth Plates Spang |
REPORT.
The Delegates are of opinion that it will conduce to clearness of statement if their Report be divided into three sections—
(1) The purpose which a lightning conductor is intended to serve.
(2) A statement of those features in the construction and erection of lightning conductors respecting which there has been, or is, a difference of opinion, and the final decision of the Conference thereupon.
(3) Code of rules for the erection of lightning conductors.
Section I.—The purpose which a Lightning Conductor is intended to serve.
A flash of lightning is the passage of an electric spark between two bodies oppositely or unequally electrified, and between which the difference of electric pressure or potential is sufficiently strong to break across the air space which separates them, and to produce what is known as a disruptive discharge. A flash may pass either between one cloud and another, or between a cloud and the earth. In the former case damage is not likely to be done, in the latter damage is or is not done, according to the point at or from which the lightning strikes. The more any object projects above the general level, the less is the distance between it and the cloud, and as the less the distance the less the resistance offered to the discharge, high objects are, cœteris paribus, most frequently struck. Some substances, such as copper or iron, can conduct a large quantity of electricity with facility, and are called good conductors. Other substances, such as living vegetable or animal matter, offer much obstruction, and form only partial conductors; while dry earth, stone, and wood almost entirely prevent the passage of electricity, and are very bad conductors—in fact, insulators.
For instance, a man may with perfect impunity clasp a copper rod an inch in diameter, the bottom of which is well connected with moist earth, while the top of it receives a violent flash of lightning. But if the electricity does not find a path prepared for it, it will utilise such partial conductors as may be reasonably near, for example—the heated air from a kitchen chimney, the soot inside, and then the metal range at the bottom; here, however, stone or dry material is generally found, which will not conduct it, and then it dashes across the kitchen at some gas or water pipe, or some pump or drain leading to damp earth, doing serious damage on the way: or it may meet some tree in its course and rend it from top to bottom, and if the human body intervene life may be destroyed. Mechanical injury is inflicted