AND LIGHTNING CONDUCTOKS. 



71 



The stones of this spire were held together by copper 

 cramps secured by lead, the best plan possible for insuring 

 its destruction by lightning : and the facilities for such an 

 event were still further increased by the lodgement of long 

 strips of lead amongst the stones, which had been poured 

 into the crevices whilst fastening the cramps. The upper 

 part of the spire was so unstable at the time I was examin- 

 ing it, that it vibrated with every movement of the foot on 

 the uppermost stage of the scaffold, and a blow by the 

 hand on the shank of the cross would make the whole spire 

 tremble. The principal rents which the lightning had 

 made in the spire, were diametrically opposite to each 

 other ; some of them were about 24 feet long, but not very 

 w^ide. I took several of the strips of lead out of the 

 damaged masonry, some of which weighed a pound and a 

 half. 



38. Oblique discharges of lightning being phenomena of 

 comparatively recent notice, the electricians of the last 

 century had no means of contemplating their effects. They 

 form a novel feature in Atmospheric Electricity, and, in a 

 practical point of view, are of vital consideration. In the 

 Memoir already alluded to (35), I pointed out the probable 

 consequences of oblique discharges of lightning when fall- 

 ing on the rigging of vessels in the masts of which are 

 fixed conductors, in the manner adopted in the Royal 

 Navy. The following are the remarks I then made : — " It 

 will be obvious that an oblique flash of lightning striking 

 into the rigging could not arrive at a conductor let into 

 the after-side of the mast, without damaging the mast 

 itself, unless it proceeded from a cloud astern* the vessel. 

 Were lightning to strike any of the yard-arms in order to 

 arrive at a conductor, that yard-arm would receive as much 

 damage as if no conductor had been in the mast ; and it is 



* This expression was intended to comprehend the whole of the arch 

 abaft the beam. 



