Experiments concerning the different efficacy of pointed and blunted rods, in securing buildings against the stroke of lightning / [William Henley].

  • Henley, William.
Date:
1774
Catalogue details

Licence: Public Domain Mark

Credit: Experiments concerning the different efficacy of pointed and blunted rods, in securing buildings against the stroke of lightning / [William Henley]. Source: Wellcome Collection.

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    ■*% I cannot avoid taking notice, in this place, of feme appearances, upon the iron conductors on St. Paul’s cathedral, fuppofed to have been the effeCts of lightning ; of which an account hath been given to the Royal Society, by a very inge¬ nious and worthy member, of whofe candor I would willingly think too highly, to fuppofe he can be offended, if my opinion concerning thefe appearances fhould be different from his. In the firlf place, had thofe bars been heated to a red heat fo inftantaneoufly, it feems probable, that the moiflure in the ftone, which almoft furrounds a confiderable length of them, at each end, where they are inferted in the pavement, would have been turned to fleam; and, adding like gun-powder, would have exploded, and driven out the bars with great violence. Alfo the leaden pipes, particularly the ends of them which are in contaCf with the iron b.ars, mu ft have been much melted ; but thefe I carefully examined, and could not perceive, that they had been at all affeCted. Secondly, the end of the iron bar, fuppofed to be the moft affefted, was not in contaft with the lead-work below it, by near two inches; yet it had no appearance of fufion, as it certainly would have had, if fo large a quantity of eleClricity had palled through it ; the ruft likewife, I think, would have been cleared away, which was not the cafe, and the end of it have been left quite bright. As to the hole through the dirt, mentioned by Mr. Gould, which lay adjoining to it; the dirt lying in a perpen¬ dicular direction, I am inclined to think, that the rain-water had foaked through it, and not w^alhed