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of the building: for it is apprehended the great church of St. Paul's, to compleat the partial conductors (which are the metallic cross, ball, gallery, dome, &c.) and secure it effectually, would require a bar of metal two inches diameter, if not more: and a building like the British Museum, one considerably less. But it appears there is no occasion for any at that repository, as it is already provided, though from accident, like many other buildings, with very effectual conductors. The copeings of the roof thereof, and the several spouts, which are continued from thence into the ground, being all of lead.
That conductors ought to be thicker than is generally imagined, seems to appear from a late instance taken notice of in St. Bride's church by Mr. Delaval and Dr. Watson, where an iron bar two inches and a half broad, and half an inch thick, or more, was bent and broke asunder by the violence of the lightening.
The Eddystone Lighthouse, which stands upon a rock surrounded by the sea, the work of Mr. Smeaton, was thought to be an object very likely to suffer by lightening; and the more so, as the top of it consisted of a copper ball two feet in diameter, with a chimney of the same metal, passing through it down to the second floor, but no further. Directions were therefore given to make a communication of metal from the lowest part of the copper chimney down to the sea; which was executed accordingly about the year 1760, or soon after the building was finished. Now if, instead of the copper ball, a pointed bar of metal had been put in its place, or above it, and communicated with the conducting matter below, there is no saying what might be the consequence of
