Abbildungen der Seite

"twinkling of an eye." Some were precipitated into the water, and others, lying dead across the boom, continued in the posture they had assumed before the accident took place. This happened on board a seventy-four at Port-Mahon, at a time when all her yards were manned in the operation of furling sails. It does not accord with my recollection whether her conductor was in use or not; but if any real dependence is to be placed on such a contrivance, it appears probable that one only is insufficient.

There are, however, opposite opinions as to the merit of this apparatus, as well as of the propriety of its being used at all; and I do not remember, in spite of repeated accidents, that either the Board of Admiralty, or those great seamen and commanders of the Mediterranean fleet, Lords Nelson, Collingwood, and Exmouth, ever did enforce any general regulation on the subject.

'A conductor at the maintop-gallant mast-head can only be looked upon as an agent more powerful than the mast itself; but by no means calculated positively to draw within its own influence every portion of electric matter which may have come first in contact, or in near appulse, with any other point; and although the mast-head is almost invariably the first to suffer, yet it is within my own knowledge, though I was not actually present, that several men, in the act of withdrawing their washed clothes from the main rigging, were killed and scorched by the descent of the electric fluid.

'It would be not only curious, but useful to ascertain, if possible, the following circumstances:-1. How many ships have been struck with lightning, out of a given number in a given time? 2. What has been the loss of lives, the extent of damage, and the expense of repairs? 3. How many of these ships were habitually in the practice of using conductors ? and 4. Did any of the ships, having them in use, suffer from the effects of lightning, and in what manner?'

These valuable observations and suggestions Lord Napier was, in 1823, advised to communicate to the public; and it must be peculiarly gratifying to the friends of this modest and unassuming, but well-informed nobleman, to find that they have, to a great extent, been carried into effect.*

[ocr errors]
[ocr errors]
[ocr errors]

*Mr G. J. Singer appears (Elements of Electricity, published in 1814, Part III. chap. i. pp. 225 6) to have entertained similar views. Conductors,' says he, for ships have been made of chains, (which are highly improper,) and of copper wires, which are easily attached, but they are with equal ease detached; and I have been informed by several captains, that many ships furnished with such conductors keep them in an inactive state, packed up below during long and hazardous voyages. For this reason, it would be better that fixed conductors should be employed they might, I should conceive, be attached to the mast; and ⚫ where motion is required, an interruption might be made in the inflexible conductor, and its parts be connected together by a length of spiral


Without any knowledge of Lord Napier's views, Mr Harris had been directing his attention to this important practical application of his electrical knowledge; and, so early as 1820, he submitted to the Lords of the Admiralty, through the Comptroller of the Navy, a proposal to make the masts themselves virtually lightning-conductors, by incorporating with them a 'double set of copper plates, in such a way as to produce an 'elastic metallic line along their surface, capable of resisting 'any strain which the spars themselves could support; and, finally, to connect these plates with bands of copper, leading through the side under the deck-beams, and with the large bolts 'leading through the keels and keelson, and including all the ' principal metallic masses in the hull.'

[ocr errors]

This proposal attracted little notice, perhaps as being beyond the comprehension of the persons to whom the government of the Navy of Great Britain was entrusted. Mr Harris, however, and his scientific friends, influenced by a love of science, as well as by a regard for human life, continued to press his invention upon a reluctant Board; and after a favourable Report by a Committee of the Royal Society, and a siege of nearly nine years, the Admiralty was induced, chiefly through the instrumentality of Sir T. Byam Martin and Sir George Cockburn, to make trial of Mr Harris's conductors. They accordingly, after 1830, fitted up above thirty ships with pointed conductors fixed in all their masts, which were stationed in the Mediterranean, the East Indies, at the Cape of Good Hope, and the coast of Africa; in South America, in North America, and the West Indies; and in the Channel, and on general service. These ships have been exposed to severe thunderstorms; and though heavy discharges of electricity have fallen upon them, yet in no instance, between 1829 and 1842, have they experienced any damage or inconvenience. One of them, furnished with Mr Harris's conductors, the Dryad frigate, was in 1830, when off the coast of Africa, struck by lightning in a tornado. The discharge fell on both the fore and main masts ' with a loud whizzing sound, and the ship appeared enveloped ' in flames.' In other cases, such as that of the Asia and Druid frigates, struck in 1831 and 1832, the electrical explosion passed safely along the conductors into the sea.


During the same period in which these thirty ships have been protected by their lightning-conductors, about forty-one, not similarly defended, are known to have been struck and injured.

wire, which would be at once perfectly continuous, and sufficiently flexible to yield to every necessary movement.'.

We may, therefore, consider this great experiment as establishing beyond a doubt the practical value of Mr Harris's system of protection. The Admiralty, however, still declined to introduce these conductors into the Navy, as a necessary part of the equipment of each ship of war. A line-of-battle ship has been valued at £120,000, and yet £100 was grudged for defending this noble and costly machine, and protecting the lives of the many hundreds of brave and skilful men employed in, and necessary to its uses!

In 1839, however, a great step was made in the promotion of this desirable object. Lord Eliot had the honour of bringing the subject before the House of Commons in the month of April; and after a short discussion, it was agreed to appoint a Naval Commission to enquire into the best method of applying conductors to our ships of war. This Commission was composed of men of science, naval officers, and other qualified persons; and, after a careful investigation, they drew up a very valuable Report on the subject, full of useful evidence, both oral and documentary. The Report was laid on the table of the House of Commons, and, in February 1840, ordered to be printed. It contains much important information, and establishes, beyond all question, the propriety of supplying every vessel with suitable conductors. Every search,' says the Report, has been 'made for cases of injury sustained by ships fitted with (Mr Harris's) conductors, and though several statements to that ' effect have been brought under our notice, not one has been sub'stantiated.'


[ocr errors]

In the very year before the appointment of this Commission, the East India Company had been led to believe, upon most erroneous representations made to them by some of their officers, that buildings furnished with conductors were more frequently struck with lightning than those which had no such protection; and, on the faith of these representations, they actually ordered the lightning-conductors to be removed from their powder-magazines, and other public buildings! This took place in 1838; and, as if to give them a practical example of their folly, one of their powder-magazines at Dum Dum, and a corning-house at Mazagon, were struck with lightning and blown up. It is not difficult to understand how an ignorant and superstitious observer should regard a conductor as inviting or attracting the dangerous element into his dwelling, when, if allowed to take its own way, it might have remained in its thunder-cloud, or pursued a different path; but when a series of well-authenticated cases, within the reach as well as the apprehension of ordinary men, clearly establish the general fact, that buildings

which had been frequently damaged by lightning, never experi enced any of its effects after they had been properly protected; and that ships with conductors defy the thunderbolts even of the tropical regions, it must be superstition, and not knowledge, that refuses to receive their aid. There are thunderbolts, doubtless, which pursue their determined course, and strike a building even in the vicinity of its conductors; but this very fact, while it proves the inability of the conductors to divert the fireball from its course, proves also their inability to attract or invite the meteor. In place of being active instruments which drive or draw the lightning into their substance, they are but passive fire-drains which afford it a free and hospitable channel-carrying it off slowly and silently when it is slowly and silently evolved, or allowing it to rush along when this is the shortest and readiest passage to the unchained and accumulated electricity. • Such 'conductors,' as Mr Harris well observes, can no more be 'said to attract or invite a discharge of lightning, than a watercourse can be said to attract the water which flows through it ' at the time of heavy rain.'



The Naval Commissioners deemed it proper to dispel, by means of facts, the vulgar prejudice that conductors attract to themselves lightning, which, had they been absent, would not have been elicited. They state, that the instances of accidents to 'ships without conductors, and the comparatively rare occurrence of lightning being observed to strike on a conductor, negative 'the above supposition.' The instances, too, of ships without conductors, having been struck by lightning in the presence of ships furnished with them, which were not so struck, are so numerous, that we have the most complete evidence both of the little influence excited by such conductors in inducing or ' attracting an explosive discharge, and of their efficacy in harmlessly and imperceptibly conveying away electricity to the


The Commissioners conclude this interesting Report with the following words ::- We again beg to state our UNANIMOUS opinion of the great advantages possessed by Mr Harris's conductors above every other plan; affording permanent security, at all times and under all circumstances, against the injurious ' effects of lightning; effecting this protection without any nautical 'inconvenience or scientific objection whatever, and we therefore 'most earnestly recommend their general adoption in the Royal Navy.'

[ocr errors]

One would have thought that Mr Harris's difficulties were now over. A Royal Society Committee-nay, an Admiralty Commission, acting under the authority of Parliament, had, with one

voice, recommended his conductors; and yet some counter-influence was at work, striving to resist authority as well as to subvert truth. All the ships fitted up with the new conductors had returned safe, and uninjured by the thunderbolts to which they had been exposed; yet, when these ships were paid off, the conductors were torn from the spars and thrown aside as old copper, instead of being replaced in other ships! This summary and practical rejection of the new conductors happened, we are sorry to say, under a Whig administration, when Sir James Graham was First Lord of the Admiralty. Mr Harris, however, renewed his application when Lord Minto was placed at the head of that Board, and had it not been for the defective state of our finances, his plans would, we believe, have been instantly adopted. Although Lord Minto could not, in the then state of the treasury, press the introduction of an improvement involving a considerable expenditure, he freely acknowledged the value of the invention; and ordered the conductors to be replaced in some of the large class ships. In order to save expense, we presume, the plan was (most improperly) taken entirely out of the hands of the inventor;' and about the same time, a sort of cheap modification of it by, a Mr Edye, patronised by the Surveyor of the Navy, was ordered to be submitted to trial. The Commission, however, decided against its adoption; and in 1842, the Admiralty may be said to have been compelled to save the British navy from lightning. Mr Harris's plans were adopted; he was allowed to superintend their execution; and his conductors are now constructed in a cheap, expeditious, and effectual manner in all her Majesty's dockyards.


Having thus given our readers some account of the ancient and modern history of lightning-conductors, and of Mr Harris's successful attempt to introduce his new system of protection into the British navy, we shall now proceed to give a popular account of the nature of thunderstorms; and a brief description of the best method of defending buildings and ships against their destructive assaults.


The production of free electricity during the conversion of water into vapour or steam is so rapid and abundant, that an apparatus called the hydro-electric machine has been recently constructed, in which the electricity is derived from steam. earth's atmosphere is, therefore, in reality a huge hydro-electric apparatus, by which free electricity is constantly generated during the conversion of water into vapour; and the electricity thus liberated is increased or modified by the condensation of vapour into rain, by its congelation in the form of hail or snow,

« ZurückWeiter »