440 PHILOSOPHICAL TRANSACTIONS. [aNNO 1778. 



the Pantheon, which was 155 feet long and l6 in diameter, had been properly 

 insulated, and there had been several cylinders properly mounted to have charged 

 it, he would have found the striking distance, and his other experiments, very 

 different from what he did, particularly those where his substitute was fixed about 

 14^ inch from his large artificial cloud. 



I must beg to intrude a little more on your time to remark on that part of 

 Mr. Wilson's paper, where from his experiments he seems to conclude, that the 

 lightning at Purfleet first struck on the point of the rod of the conductor, and 

 then, by a lateral part of that stroke, struck the cramp on the coping stone. I 

 believe, if he had examined the situation of the stone, and the place where the 

 cramp was struck, he would have found, that if the lightning had struck on the 

 point of the conductor, that to have produced that effect on the stone, it must 

 after it had struck on the point, and passed down a quantity of metal, have 

 struck from the metal up into the air, then down again on the cramp, and then 

 again to the metal it had left, for the small dent or hollow made by the lightning 

 was on the upper surface of the stone, and yet the metallic communication to the 

 earth continued from the point under the stone which was struck. It appears 

 more probable to me, from the trifling damage it did, that the charged cloud had 

 passed over the pointed conductor, and had been exhausted of a great part of its 

 electricity in passing; and that after it had passed, it was attracted down lower by 

 a ridge of hills that was beyond, and that the cloud being out of the influence 

 of the point to prevent its striking, the end of the cloud might strike at an 

 angle in the cramp, and so to the metallic part of the conductor, which was only 

 about 7 inches below. I shall conclude with observing, that Mr. Henly and my- 

 self had the pointed rod of the conductor at Purfleet taken down to examine the 

 point ; but we found no appearance on it that showed that it had been struck. 



XXXVl. Reasons for Dissenting from the Report of the Committee appointed 

 to consider of Mr. Wilsons Experiments; including Remarks on some Experi- 

 ments exhibited by Mr. Nairiie. By Dr. Musgrave, F. R. S. p. 801. 

 I do not find that Dr. Franklin, in any of the passages where he speaks of the 

 efiicacy of sharp-pointed conductors to prevent electrical explosions, has expressed 

 any doubt of their being universally preferable for this purpose to those which 

 have a blunt or spherical termination. The same observation may be made of 

 the other gentlemen who are the advocates for his doctrine. It may therefore 

 be assumed, that both he and they mean to assert a universal proposition, " That 

 sharp points will, in all cases, draw off tlie electrical fluid silently, within the 

 distance at which rounded ends will explode; or, at least, that the former sort 

 will in no case receive an explosion at a greater distance than the latter." Though 

 I dissent from this doctrine, I do not mean to assert the contrary universal pro- 



