earth plate on to same, or sometimes employ a large gridiron made of copper tape, using as much as 200 lineal feet in its construction. Wherever we make earth terminations in rocky, dry, or gravelly soil, we always fill in with a load of small coke, charcoal, or other carbonaceous matter, and also divert the rain fall-pipe system over the termination so formed; also, wherever possible, we connect the conductor with the gas and water systems outside the building. In all cases of earth terminations, the size of earth-plate is in proportion to the size of conductor employed, and other circumstances.
VII.—We are unable to come to any conclusion as to any definite area which one lightning conductor will effectively protect, and no two writers appear to agree on the subject; but from actual practical experience of 30 years, combined with the closest observance and research, we are in the position to say, emphatically, that a conductor on one prominent elevation—for example, a turret will not protect a similar elevation, be it only 1 yard, or 50 yards distant; but that providing that two prominent features be provided with a conductor point on each, then on the same foundation, we say that both of them would be effectively protected. But for the purpose of simplifying and practically illustrating our views on this subject, we enclose you tracings and particulars of several buildings for which we have designed the system of lightning conductors, and which we believe to be perfect.
VIII.—Yes—always, and in proportion to the number of extra terminals adopted.
SANDERSON & CO.
DETAILS OF LIGHTNING CONDUCTORS APPLIED TO NOTTINGHAM CASTLE.
The following three engravings render very few verbal details necessary. Fig. 1 gives the east elevation of the castle, it shows part of a flag-staff 115 feet high, which has a conductor, also three of the principal terminals, and twenty-six minor points upon the building, and by two dotted lines the position of two of the main conductors to earth. The principal terminals are tapered iron tubes, 13 feet long, carrying copper tapes 1 inch × 1/16th and terminating with copper points tipped with platinum; the minor points are of solid copper 9 inches long. The main conductors to earth are copper tapes 2½ in. × 1/16th.
Fig. 1.
Fig. 2 give a plan of the roof, much of which is of glass with wooden rafters. The twelve principal terminals are shown by small rings, the ninety-four minor points by round dots, the horizontal copper tape (2 inches × 1/16th), uniting all the upper terminals, by a pecked line, and the position of the main conductors to earth by dotted crosses. All the gutters are metallically connected with the conductors.
Fig. 2.
Fig. 3 gives a general plan (for which we are indebted to the architects, Messrs. T. C. Hine & Sons) of the castle and grounds, and also a little section indicative of the precipitous eminence on which the castle stands. From these it will be seen that two of the main conductors to earth are carried underground at a depth of about 4 feet, under the terrace and down the slope and terminate in trellis-work, about 14 feet square, of 2½ inches × 1/16th copper tape rivetted at every intersection. The other earth contact is obtained by bolting the terminal on to the town water-main. The total length of tape used in the earth connections was about 500 feet.
SANDERSON & CO.
Fig. 3.
APPENDIX D.
REPORT OF THE REPRESENTATIVES
OF THE
ROYAL INSTITUTE OF BRITISH ARCHITECTS
TO THE
LIGHTNING ROD CONFERENCE.
The Council of the Royal Institute of British Architects sent out upwards of 600 circulars (a copy of which follows this Report) to their Architectural Members requesting information as to injury by lightning to any buildings known to them.
The Council also requested the same information from their Honorary Associates (upwards of 100 in number), who are chiefly men eminent in the Scientific, Literary, and Artistic world.
The Council have received up to this date only 35 answers from Architects, and 1 from the Honorary Associates.
Of these answers many are to the effect that no case of injury has arisen to works under their direction. The remainder give 33 instances of damage, and enter, in many cases, very fully into the details of them.
The instances given may be roughly classified thus:—
There are 26 of buildings injured where there were no conductors.
In 9 of these the lightning did some injury to the chimneys and other exposed parts, and was then conducted safely to the ground through the metal gutters and rain water pipes.
In three other instances the lightning appears, from the statement of persons in the building struck, to have dispersed and passed out by open doors, &c.
We give no opinion as to this, but the facts are distinctly stated. In several other cases the lightning passed off in several distinct directions and currents.
There are 6 cases of buildings being injured although protected by lightning conductors. In one of them (No. 14) the failure is clearly explained by the fact that the lower part of the conductor had been stolen, leaving only two or three feet of it in the ground. The lightning in this case broke through a wall 4 feet 6 inches thick, at a height of 6 feet from the floor to a gas pipe.
In another case (No. 3) a gable was struck, although close to a spire and turret which had a lightning conductor.
In another (No. 7) the part struck (a chimney) was 64 feet away from a tower, in the same building having a lightning conductor.
In No. 24 the conductor was sufficient protection until it passed at a sharp bend round some mouldings; these it injured, but did no further damage.
In two cases (Nos. 21 and 23) the discharge injured some gas tubing near it, and set fire to the gas, and by its means to the building.
We beg finally to call attention to the drawings attached to No. 7 (Mr. Colson, of Winchester), showing the injury to trees 130 feet away in a direct line from a spire which was destroyed, it having no conductor.
T. HAYTER LEWIS, V.P.
JOHN WHICHCORD, V.P.
CIRCULAR.
Lightning Rod Conference.
Sir,
