found that it arose from a storm or gale in the Atlantic, between the meridians of 20° and 40°W. The prevailing current near this coast remains, however the Carribbean or N.W.b. W. current. Last month afforded another instance of it. The brig Campbell of Liverpool, lost her boat off the River Nizao, and it was within a very few days afterwards picked up at Petit Trou.

Santo Domingo, March, 1852.

ROBERT H. SCHOMBURGK.

REVIEW OF THE HISTORY AND PROGRESS OF A SYSTEM OF PErmaNENTLY FIXED LIGHTNING CONDUCTORS FOR H.M. SHIPS-FROM THE YEAR 1820, WHEN FIRST PROPOSED, TO the present Year 1852, WHEN FULLY ADOPTED INTO THE PUBLIC SERVICE.-By Sir W. Snow Harris, F.R.S.

(Continued from page 257.)

14. The proposed application of a permanently fixed system of metallic conductors to the masts and throughout the hulls of H.M. Ships with a view to their effectual preservation from lightning, consists as we have seen (10) in completing the conducting power of the general fabric to the greatest possible extent, so as to bring it into that comparatively passive or non-resisting state it would assume, supposing the whole mass to be metallic throughout. This method of guarding ships from lightning evidently embraces the most advantageous form under which marine lightning conductors could be possibly applied, for it must never be forgotten in our reasoning upon this question, that the material of the masts and hull of a ship is already what may be termed a conducting substance up to a certain point, that is to say it can always transmit a large quantity of electricity under a current form. (9) Now by incorporating with this material continuous and capacious lines of metal, that is by making our conductors an integral part of the ship itself, we enlist as it were into the service, the conducting power which the masts and hull already possess, by adding it to that of the metals, and thus convert into an auxiliary source of safety, what might otherwise become a source of damage. The masts especially, as is evident, are calculated by their mere position alone to determine the course of electrical discharge through the hull, and will always do so under any circumstances to a greater or less extent, even though a conducting chain be applied to the rigging. The position in which the masts are necessarily placed is therefore so far a perilous one, and unless their conducting power be fully completed by the aid of metals, damage may arise. No temporary form of conductor of small capacity, such as a small rope of wire, or a chain, partially applied as rigging can ever completely meet this difficulty.

be

15. In the first attempt to carry this system fully into practice, many and very serious obstacles presented themselves, as may readily conceived. It was for example required so to arrange and fix the conductors in series, as to preserve a perfectly jointed line, and at

the same time a line not liable to become deranged by any strain or flexure which the spars could support: the series was at the same time required to be so perfect as entirely to preclude that violent expansive action commonly attendant on heavy discharges of lightning, and which not unfrequently distorts and twists very large iron rods; indeed the difficulty of satisfying these conditions, appeared to many practical sailors well acquainted with the severe strain to which a ship's mast is subject under the pressure of sails, so great, as to lead thein to consider the plan as next to practically impossible.

*

16. The conditions of flexibility and continuity of the conductors were provided for, in the way figured in the Nautical Magazine, for the years 1834, and 1837, that is to say, by constructing the series of narrow plates of copper sheet in lengths of four feet, placed in two layers, one immediately over the other, and in such a way as to allow the butts or joints of the one series to fall immediately over or under the continuous portions of the other, the series of joints being rivetted at the butts throughout the line. We have thus an alternating series of shut joints producing a perfectly continuous and flexible line of conduction. The conducting series thus arranged had now to be incorporated with the spars and led throughout the hull, and connected in various directions with the copper expanded over the bottom of the ship and with the sea; as indicated in the plans already given in the volumes of the Nautical Magazine just referred to. The incorporation with the spars presented some difficulty, which was finally overcome by laying the plates in shallow grooves cut for their reception along the aft sides of the respective masts from the truck to the keelson; and preserving an adequate connection in the caps through which the upper portions of the masts were required to slide. The plates were at first fixed to the spars by screws. The heads of these however soon twisted off and the plates as predicted became displaced. A short strong copper nail was now substituted by which the plates were pretty well secured, and were in this way applied to H.M. Ships Druid, 36, Dryad, 36, Blanche, 36, Forte, 44, Spartrate, 74, Asia, 84, Caledonia, 120, Revenge, 74, Sapphire, 28, and Acteon, 28, to these were added the Beagle, 10. All these ships were eventually employed on foreign stations; the last named vessel the Beagle was sent under the command of Captain Fitzroy, to the South Seas on a dangerous and difficult survey, and was on more than one occasion effectually preserved by the conductors.

17. From the circumstance of this method of lightning conductors for ships under the form of metallic plates being altogether a new and unpractised experiment, considerable expense and delay was almost certain to embarrass its progress. Thus the grooves in the spars, for the reception of the plates, instead of being speedily and accurately cut out by proper planes as now done, were at first formed by means of chisels and the hand, a slow and tedious process. The plates also instead of being cut parallel and with rapidity from copper sheet by a circular saw, and drilled for the fixings by machinery, were also cut by hand in the smith's

* See plates, in these volumes.

any

shops, or by shears. Even the nails for fixing were produced from copper bolt instead of being furnished at a cheap rate by contract. All this would necessarily involve some very considerable outlay, and would furnish severe objections to the use of such conductors on the ground of finance; objections which the opponents of the measure did not fail to employ with the utmost rigour. The consequence was, that although it was well known that the system had upon the whole done good service in defending the ships just named from lightning, yet no public reports ever appeared. The whole invention was quietly discountenanced. The conductors as the ships returned from their period of service, were taken out of the masts, and thrown aside as old copper, and the whole system completely abandoned: and that too without kind of investigation of its merits as determinable by experience in the ten vessels in which the conductors had been placed or any sort of inquiry whatever. The board of Admiralty of 1837 on being applied to, professed to have called for reports from the captains of the respective ships, but no result ensued; no sort of information upon the question was ever elicited; in fact no records of any effects of lightning were forthcoming, and it was inferred that no opportunity of testing the plan had been met with. One point at issue however was clearly established;-the ships had in no way suffered from lightning, whilst of the remainder of the navy in commission during nearly the same period, above thirty sail, were known to have been struck by lightning in various parts of the world, and severely damaged. These included several ships of the line, steamers and large frigates. Thus, in November, 1832, the Southampton, a large frigate of 50 guns, was struck by lightning in the Downs, and narrowly escaped blowing up; in the Dispatch, 18, struck by lightning at sea off Cape Roca in 1832, no less than twenty men were more or less injured; in another brig, the Racehorse, struck by lightning in 1831, off Port Royal, the main-mast was ruined, top-mast shivered in pieces, all the bulkheads below deck smashed in pieces, and this sort of destruction prevailed generally throughout the navy.

18. At last in December, 1838, the Rodney of 90 guns, one of our finest ships in the Mediterranean, commanded by Captain Hyde Parker was assailed by a severe electrical storm off Syracuse. The main-royalmast vanished in chips, and the fragments covered the surrounding water. The main-top-mast was rent, and the main-mast completely ruined. Two men were killed aloft and two more severely wounded. The gear on the main-yard ignited and the ship was on fire aloft, she remained for some time in great peril, and was only saved probably from destruction, by the coolness and intrepidity of Captain Parker and his officers, and the high state of dicipline, for which, as is well known, the Rodney was remarkable. The ship was placed for the time hors de combat and was obliged to be laid up under an expensive refit at Malta at a cost to the country of certainly not less than £3,000 or £4,000 to say nothing of the services of the ship. The main-mast on examination was found charred to the heart. The case was of sufficient

• Official Letter, dated June 15th, 1837.

importance to attract the attention of the French authorities in the Mediterranean, and a report on the circumstances was in 1839, presented by Mr. Arago to the Academy of Sciences at Paris. Those who had so strenously objected to the new conductors on the ground of the expense of the plan, were now obliged to confess, that immunity from so much destruction and inconvenience to the navy, was worth purchasing at any price.

It is not unworthy of remark, that this very ship the Rodney, was fitted out and sent to sea from Her Majesty's Dockyard at Plymouth, almost at the moment that the new conductors which had done good service in similar ships, were being removed from their spars and cast aside as old copper: so that the Rodney was allowed to proceed to a station on which the dangerous effects of lightning were repeatedly experienced without any adequate means of defence whatever. Nothing the author of this paper could say, seemed to have the least effect, in preventing it. It is not unimportant in tracing the history of this question, to note this circumstance as being an instructive illustration of the difficulty with which advances in practical science not running immediately parallel with popular opinions have to contend; and with what little scruple the best ordered designs bearing on the public interest may be

cast aside.*

19. The importance of effectually guarding the Royal Navy against such destructive damage as that just described, being every day more and more apparent, Lord Eliot, now the Earl of St. Germans, thought it expedient to call further attention to the question, through the medium of the House of Commons. In the course of the debate which ensued on the 23rd of April, 1839, the late Sir Robert Peel suggested the appointment of a naval and scientific commission, to enquire and report to the house on the subject, the members to be selected by the Board of Admiralty, a proposal to which Lord Eliot at once assented. In the able and very lucid speech with which his lordship introduced the subject, the great practical results of the conductors in preserving the ships in which they had been placed, from lightning, was clearly made out. The Secretary of the Admiralty did not attempt to deny the value of the plan, but was led under a misapprehension to state as an excuse for its discontinuance, the then obsolete orders of the Navy Board nearly twenty years before, to rescind their directions for a trial of the plan in H.M.S. Java and Minden, (13) but which the subsequent determination of the Admiralty in 1829, to carry it out in the ten ships just specified, (16) had completely superseded. The Board of Admiralty, of which the present Sir C. Wood was then the secretary, did however exercise as it must be allowed, a very sound discretion in their selection of the commissioners who were to investigate and report on this most interesting question. Indeed it would be difficult to find in any country,

It is a remarkable fact, highly illustrative of the difficulty of introducing new inventions into use, that the prejudice in favour of the old backstaff, by which the sun's altitude was obtained at sea, occasioned considerable delay in the adoption of Halley's Quadrant among seamen, now his most favourite instrument.-ED.

men more eminently qualified for the task, whether considered as practical sailors or as men of science. The commission consisted of Rear Admiral Griffith, Admiral Sir James Gordon, Captain Sir James Clarke Ross, Mr. Fincham, master shipwright of the Chatham dockyard, and Professor Daniell, of King's College. Mr. Waller Clifton, the private secretary of the secretary of the Admiralty, acted as the secretary of this commission, so that the investigation was altogether in the hands of the Admiralty, or at least of very distinguished and well qualified persons, especially recognized by the first Lord of the Admiralty as fit and proper persons to conduct it.

20. The commission commenced its sittings at Somerset House, on the 3rd of June, 1839, and terminated their enquiry on the 9th of July following. In the course of this time, the commissioners called in evidence the several officers who had been in command of the ships in which the new system of conductors had been applied, and collected a large amount of interesting and valuable information from other naval officers who had witnessed the effects of lightning at sea. They also invited the opinions of scientific men best acquainted with electrical science, Faraday, Wheatstone, &c.,-they examined the papers left on this subject by the late Dr. Wollaston, and Sir Humphrey Davy, and enquired fully into the practical and scientific merits of other temporary forms of lightning conductors for ships, such as chains, linked rods, and ropes of wire. Upon the whole evidence, however, before them, they arrived at the conclusion, that a capacious system of permanently fixed conductors such as we have adverted to (10) is the only effectual security for the royal navy from lightning.*

21. It further appeared in evidence in the course of this enquiry that the plan had been perfectly successful, and that although no official reports had hitherto appeared to this effect, yet the fact itself was fully elicited from the officers who were in the several ships. Commander Norcott states that at Rio, "awful lightning was conducted down the fore and main-masts of the Druid, but that no part of the mast was injured."+ Commander Turner stated that, in H.M. ship Dryad, on the coast of Africa, "the ship appeared to be enveloped in flames, that the fore and mizen-masts were struck, but sustained no injury." Captain Fitzroy reports, that the Beagle, whilst under his command was "twice struck by lightning, but experienced no damage." Several men saw the lightning fall on the masts, &c.,-other evidence was elicited to the same effect; all this is valuable in a general history of any scientific invention, as tending to show the great importance of an untiring and steady perseverance in the cause of truth. But for this a large body of facts very important to science, would in this instance have been entirely lost sight of, and an effectual means of preserving the navy from lightning suppressed.

22. These facts also, very completely refute an opinion gratuitously offered to the Board of Admiralty, by Mr. Martyn Roberts, with a view

* Report—Shipwrecks by Lightning, 11th February, 1840, page 15.

† Report p. 94, 29, 28.