VOL. LI v.] PHILOSOPHICAL TRANSACTIONS. 13Q 



at Newbury in New-England, that though a small wire was beaten to pieces by 

 lightning, and dissipated by its force, the rod of a pendulum conducted the 

 whole without being melted or otherwise injured by it ; and that, great as the 

 quantity was in this instance, and which utterly destroyed the small wire, no 

 damage was done to the building, as far as the small wire and the pendulum of 

 the clock extended : and in the remarkable instance mentioned by Mr. 

 Kinnersley in his* letter to Dr. Franklin, where a brass wire of about 2 lines 

 thick, 10 inches long, and terminating in a very acute point, was inserted into 

 the iron rod, about 2 inches and half only of its top were melted by the light- 

 ning; the remaining part of it transmitting the lightning without being fused 



by it. 



You will observe in this disquisition, that I have no where mentioned the ap- 

 paratus attracting the lightning. I have avoided introducing the term attraction 

 here, operating as an active principle ; as I consider the apparatus purely passive, 

 and only affording, from the aptness of its parts to that purpose, an easy and 

 uninterrupted passage to the lightning, and thereby preventing its violent 

 efforts. 



You will pardon, Sir, this long digression in relation to St. Bride's church ; 

 as it gives so positive and explicit an answer to part of your 7th question ; such 

 a one as could not, without the late thunder-storm, have been furnished, at 

 least from hence: to wit, that without a proper apparatus, weather-cocks 

 placed at the tops of any buildings are dangerous to them in thunder-storms ; 

 but more especially to powder magazines. The accidents which have lately 

 happened to St. Bride's and South Weald churches, if considered as great elec- 

 trical experiments, furnish very important, and, I flatter myself, useful conclu- 

 sions. They are too hazardous and expensive however, to wish to see often 



repeated. 



If the erecting of an apparatus of this sort should become general in countries 

 where thunder-storms are frequent, and often attended with mischief, though 

 damage should be really averted by it, the operation of the apparatus would be 

 unseen, and therefore unknown, unless in such rare instances as that mentioned 

 by Mr. Kinnersley. To make its effects apparent, as has been hinted to me by 

 Dr. Heberden, a very deservedly eminent physician here, if chains are employed 

 as metallic communications, instead of wires or rods, whenever the lightning 

 comes near enough to affect the apparatus in a considerable degree, it will, with 

 out mischief, be visible in the dark, by its sparkling and snapping in its passage, 

 at the links of the chain. The effects of the apparatus may be observed in 

 another manner. If the metallic communications are by the means of a wire 



• Phil. Tsans. abridged, vol. xi. p. 702. 

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