138 PHILOSOPHICAL TRANSACTIONS. [aNNO I764. 



What happened to St. Bride's cannot but give us some apprehensions for that 

 noble edifice St. Paul's. This is above 100 feet higher than St. Bride's, and 

 therefore more in the way of accident from thunder-storms. On its magnificent 

 lantern is placed a cross of metal, which is inserted into the stone of the 

 lantern ; and this is supported by a tnmcated cone of brickwork, which arises 

 from the arches of stone below. The cupola is covered with lead, which is 

 continued to the spouts of the same material. These bring down the water to 

 the stone gallery under the cupola, and end within about a foot of the stone. 

 From hence the water is conveyed a considerable distance, in a stone trough or 

 channel, to the leaden spouts; and these are carried down the building, and 

 terminate, as I was informed on inquiry, in the common sewer. By this ar- 

 rangement the metallic communication is interrupted. In thunder-storms 

 during rain, the water carries off in its streams the electricity, as perfectly, as 

 the most complete metallic communication would ; but when there is no rain, it 

 is otherwise ; and these interruptions are the great cause of danger. To lessen 

 which, as far as we can conclude at present, it would be expedient to make, by 

 the means of several copper wires, small rods, or pieces of lead, a metallic 

 communication between the gilded cross, and the lead of the cupola : and again, 

 from the leaden spouts of the stone gallery to those which bring the water 

 thence ; care being taken that from the bottom of these last there should be a 

 metallic communication, if there should be found to be none at present, with 

 the water in the common sewer. Thus, without much expence, a complete 

 metallic communication may be made between the top of St. Paul's church and 

 the water ; which had it been done at St. Bride's, the ravages so lately expe- 

 rienced had in all probability been prevented. 



From considering the circumstances of this thunder-storm, I cannot but be 

 of opinion, that the injury done to St. Bride's prevented mischief to St. Paul's. 

 St. Bride's is a very high building, and within a small distance nearly west of 

 St. Paul's. When this distance is considered, and that the lightning came in 

 the direction of St. Bride's to St. Paul's, and that when the thunder-cloud came 

 near the former, it exploded there, and parted with much of its force ; what was 

 left did no damage to the latter, though the much higher and more exposed 

 building, and having a metallic cross at its top. 



I have recommended as metallic conductors copper wires of the size of a goose 

 quill ; as, when of that thickness, they may easily be bent to any direction ; 

 andj where thought necessary, any number may be employed. I consider this 

 as a kind of standard, from what Dr. Franklin wrote to Mons. Dalibard of Paris 

 on this subject.* He observes, in a church which suffered greatly by lightning 



• See Phil. Trans, abridged, vol. x. p, 632. 



