1851 Great Exhibition: Official Catalogue: Class VIII.: William Snow Harris
150. HARRIS, Sir WILLIAM SNOW, Plymouth — Inventor.
Practical models, illustrative of the system of conductors employed to protect Her Majesty's ships, from lightning:-
1. General plan and construction of the conducting plates, showing the alternate jointing of the plates.
2. Line of conduction on the masts from the vane to the step.
3. The conductor as applied to a topmast.
4. General plan of the hull, with connecting branches and bolts communicating in various points with the sea, viz.: by the keel, at the sides; and at stem and stern.
5. Preparation of the step of the mast, with part of the keelson. This method of preserving ships against the effects of lightning has proved efficacious and it requires no care or interference on the part of the officers or crew. Since the full employment of this system in the Navy, no damage from lightning has been recorded.
Fig. 1 shows the line of conduction on the masts from the vane spindle to the step.
Fig. 2 represents the moveable tumbler at the junction with the caps, in which A D is a copper plate fixed on the cap, N M an angular plate set on the hinge C D. P the conductor on the mast. This hinge is sometimes covered with a small saddle of wood, to prevent its being damaged.
Fig. 3. The vane spindle; in which s t is the portion inserted into the royal mast: s the thread of a screw for securing it: D a thick cylindrical base, with a hole at D for a small lever.
Fig. 4. The step of the mast and portion of keelson. A B, M N the transverse and longitudinal branches passing round the step, and through the mortice at S. f c the branch over keelson; bolts a b c.
[The several nautical and scientific conditions, which this system of lightning. conductors in ships professes to satisfy, are as follow:-
The conductors are capacious, and always in place, consequently ready to meet the most unexpected danger, at all times, and under any circumstances, in which the general fabric in all its casualties may become placed. The system of conductors, whilst being permanently fixed throughout their whole extent, still admit, upon demonstrable principles of electrical action, the perfect motion of the sliding masts one on the other, or of any part of the mast being removed either by accident or design, without for an instant interfering with the protecting power. The conductors are independent of the officers or crew of the ship; so that the sailors are never required to handle or replace the conductor, often a very perilous and annoying service. The conducting plates are quite clear of the standing and running rigging: the whole series is calculated to resist external violence, and at the same time yield to any flexure or strain incidental to the spars to which they are applied. Finally, the whole system is so arranged, that a discharge of lightning falling on any part of the ship could scarcely enter upon any circuit in its course to the sea, of which the conductors did not form a part; hence should arise that perfect security which experience has shown to be derived from such a system.
In the original conception of this system, the inventor was led to consider the electrical discharge, as seen in the phenomenon of lightning, to be an explosive form of action of some unknown agency in nature when forcing its way through resisting matter, such as air, all vitreous and resinous bodies, and some other kinds of matter, whilst in traversing other bodies, offering but a very small resistance to its progress, this explosive form of action we call lightning, becomes transformed into a sort of comparatively quiescent current. The attempt was, therefore, to bring a ship, as far as possible, into that passive or non- resisting state which she would possess as regards the electrical discharge, supposing the entire mass were metallic throughout, so that, from the instant the agency of lightning struck upon any portion of the masts aloft, the explosive action would vanish, and the electrical discharge be prevented from traversing the vessel under the form of lightning. The following extract from the official journal of H.M.S. Conway, 28, whilst proving, by a great natural experiment, in common with numerous other cases, the truth of this deduction, is of no ordinary interest in practical science:—
"Port Louis, Isle of France, 9th March, 1846, 11.45 A.M. The pendant staff at main-top mast-head was shivered in pieces by lightning, Harris's conductor carrying off the fluid without further damage."
The ship was refitting at this time, and the topgallant masts on deck, so that a small spar was set up at the top-mast head as a temporary support for the pendant; this spar had not, consequently, any conductor on it. It is seen by the ship's journal, that the spar was shivered in pieces by the explosive action, which became immediately transformed into a comparatively quiescent current on reaching the line of conduction.
The report of the thunder was as if one of the main-deck guns had been fired. The gunner, who was sitting in his berth, immediately under one of the lateral branches of the conductor passing through the ship, saw, through the scuttle port, a brilliant blaze of light from the ship upon the sea, but experienced no inconvenience.]