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 365.) 43. The general adoption of the new system of permanently fixed conductors into the public service as being the only effectual security for H.M. ships from the destructive agency of atmospheric electricity, dates, as we have already observed, (27,) from June 1842, since which time the Royal Navy has been completely preserved from those terrible casualties by lightning so common in former years. For although the electrical discharge has repeatedly struck the ships in all its fury, yet no damage has ensued: the only cases of damage by lightning to H. M. ships of recent date, are a few solitary instances of vessels which, from some peculiar circumstances, were not fitted with the new conductors. It is rather to be regretted that complete details of all the various instances in which lightning has struck the ships of the Royal Navy having the new conductors, have not been generally recorded. In some instances the cases are very summarily noticed; in others they have been passed by as being of common occurrence; no damage having ensued. Nevertheless a great number of such cases are officially reported quite sufficient to prove the vast importance of the application, and its bearing on the national interests. About forty ships are known to have been preserved by the conductors in the heavy thunderstorms of foreign climates. These cases present to us a most valuable collection of facts derived from experiment upon the great scale of nature; and which completely set at rest all those disputed points relative to lightning rods, which for nearly a century have been made questions of severe, and often of bitter, philosophical controversy. Whether lightning rods attract the electrical agency? Whether they can be so applied as to afford complete security at all times and under all circumstances; and within what limits? Whether they may cause damage either by drawing from the clouds more electricity than they can transmit, or otherwise, by lateral explosions from their surface? Whether their pointed terminations either prevent altogether or greatly modify the fury of a stroke of lightning? All such questions will be now found to have received a complete solution; so that there can no longer remain any doubt upon such points. In fact, the new system of permanently fixed lightning conductors, so fully carried out in H.M. ships, embraces, in all their generalities, the great fundamental principles upon which such applications rest, (10,) and must therefore be considered as one of the greatest and most valuable experiments of its kind ever ventured on by any maritime conntry. 44. The following is a list of officially recorded cases of ships of the Royal Navy preserved, at various times, by the new conductors from the destructive agency of lightning in various parts of the world. We shall reserve for an appendix a brief summary of the attendant phenomena detailed in the same way, as in the history of those cases of ships struck and damaged by lightning not having conductors, and printed in the pages of the Nautical Magazine for the year 1843, and with which they will be found to present a marked and most important 45. The question whether lightning conductors and other metallic substances especially invite the fury of the thunder-cloud, and draw down, as it were, destructive action upon ships, which otherwise would not ensue, is very satisfactorily determined by the phenomena observable in those instances of ships struck by lightning furnished with metallic conductors throughout the general fabric, and by the course of experience as compared with other ships of the Navy struck by lightning when such conductors were not present. We have already seen that the general system of lightning conductors has been more or less in use since the year 1830, at first in about ten of H.M. ships, and since 1842 throughout the whole Navy, which gives a clear course of experiment of at least twenty years. Now during this time the ships having the new conductors have, as appears by the preceding table, been exposed to lightning in its most appalling form in almost every part of the world:-In India, China, the Pacific, the West Indies, the coast of Africa,-in fact in every latitude and climate in which electrical discharges from the atmosphere are especially to be dreaded. Taking then a clear period of twenty years, viz., 1831 to 1851, we have not above forty recorded cases in which lightning has actually fallen on ships with explosive violence; that is to say, in which the ships have been what is commonly called "struck by lightning." We have had, it is true, a very great number of remarkable instances in which the conductors have carried off tranquilly, as it were, large streams of atmospheric electricity, and so far parried, probably the dense explosions incidental to the presence of a thundercloud; but the cases in which ships have been actually struck by lightning, may be considered as limited to about forty. In no case has any ill consequence ensued. 46. If we now take a similar period for ships not fitted with such conductors, viz., from 1822 to 1842, that is up to the date at which the general system was fully adopted into the public service, and which includes ten years common to each period, we find by reference to the official records of ships of H.M. navy struck by lightning, printed in the pages of the Nautical Magazine for 1843, that at least sixty ships were struck by lightning within that same period of twenty years, being nearly one-third the average number of ships annually at sea; and in every instance destructive damage ensued, and in very many cases to a frightful extent. It appears, therefore, from this analysis, that ships not furnished with the new system of lightning conductors, have been struck by lightning more frequently than ships having such conductors, in the proportion of 3: 2, a result quite conclusive of the question, "Whether such conductors operate in attracting lightning to the ship." 47. Taking the ten years, from about 1831 to 1842, common to the two periods of twenty years which we have selected, we find that during these ten years some ships were fitted with the general system of metallic conductors, and some not; and that both classes were on service together. We have hence a farther and most important source of evidence upon the merits of this interesting question relative to lightning, so frequently and critically discussed upon abstract theoretical views and individual opinion. Now the following table includes a list of ships, not having the conductors, known to have been struck and damaged by lightning, in various parts of the world, within this period; together with the number of ships fitted with the permanent conductors in their spars and hull, and employed on the same stations during the same period, but in which no damage ensued. Of these last ships, 33 in number, not above 7 were actually struck by the electric discharge, although every one of them, as appears by the ships' logs, were frequently exposed to heavy lightning storms.* The same ship is occasionally found in both columns, from the circumstance of having been subsequently fitted with the new conductors, after having been struck and damaged by lightning. ester, 71, twiloubae Asia, 841 rw botlit que Argyle, 24 2018 797932dw Revenge, 76-hiesti 8+ Rodney, 92 qo rotor Laos Acton, 28 Images GE hoor leioillo y exeqqa quod to owl 08 J110G age 19 gols Totoobnos usa o que daud Be pathanne ada Cornwallis, 74ah sdt no This table is more particularly conclusive, from the circumstance of its involving the same ship, both with and without the new conductors. It will be seen that in the Mediterranean alone, no less than five sail of the line were struck and damaged by lightning; whilst in the ships fitted with the new conductors, on the same station, no damage whatever arose... 48. Besides this general evidence upon the question whether metallic conductors operate in drawing down lightning upon ships, we find some especial cases directly bearing upon it highly deserving attention. It appears by official records, that in March, 1840, the Asia, 84, and Powerful, 80, two of the ships included in the preceding table, were moored near each other in Vourla Bay, in the Mediterranean, the Asia being fitted with metallic conductors in her spars, the Powerful not so fitted, but unprovided with any means of continuous metallic conductors along her spars to the sea. Under these circumstances both ships were exposed to a heavy thunder-cloud, which overshadowed the surrounding sea. Now it happened that instead of lightning falling on the Asia, that is to say, the ship in which the supposed attractors were present, it struck with destructive violence upon the Powerful, not having any conductors; the fore-top-gallant-mast was shivered in pieces, the fore-topmast rendered unserviceable, and the foremast severely damaged. The Asia, on the other hand, escaped all damage, probably by the action of the conductors in rapidly dispersing the atmospheric electricity which overspread the ship. This case, therefore, presents to us a great natural experiment, which would, if possible, have been especially selected for determining the merits of the question under consideration. 49. On examining other records relative to ships of the navy fitted with the new conductors, and exposed at the same time to thunderstorms in common with other vessels, not having such conductors, we find the following important instances: H.M. ship Minden, 74, was exposed to severe thunder and lightning at Hong Kong in August, 1842, during a typhoon; two flashes struck the mainmast. The electric fluid played about the conductors, which conveyed away a fearful stream of electrical fire, attended by a loud whizzing noise. At this time the electrical discharge fell on a large merchant ship; the John Barry, near the Minden, and shivered her foremast in pieces; several other merchant ships in the vicinity were also struck, and four men killed. H.M. ship Fox, 42, was struck by a severe flash of lightning at Colombo, in the East Indies, April 5th, 1847, which was carried off without damage by the conductors. At the same instant nearly a merchant ship, the Bittern, near the Fox, was also struck, and much damaged. H.M. Southampton, during her last period of service in South America, 1850 to 1851, experienced many severe storms of thunder and lightning. Whilst off Monte Video a tremendous discharge of electricity fell one morning on the mainmast, about 5 A.M., which was transmitted without damage by the conductors. At the same time NO. 8.-VOL. XXI. 3 L |