VOL. LXIII.] PHILOSOPHICAI^^TRANSACTIONS. 3"" 



appeared the most eligible to have the conductors made of one continued piece 

 of metal only, and of an equal diameter throughout. But what that diameter 

 ought to be, depended on other circumstances, some of which are taken notice 

 of in a former paper, referred to above, which I laid before the r. s. 



By this historical sketch, we see the propriety of Dr. Franklin's introducing 

 points, and the advantage philosophy has derived from them: by ascertaining 

 that lightning and electricity are one and the same fluid: which appears to be 

 diffused every where, at least on this earth and in the atmosphere. But when 

 curiosity, which I apprehend was one of the first motives for introducing points 

 to invite the lightning, was satisfied; and experience had taught us, that we had 

 it in our power to collect that fluid which occasions it: and when the principle of 

 its action was from experiments thus investigated and ascertained, this matter of 

 invitation, viz. by using points, ought, in my opinion, to have ceased;* because 

 a greater quantity of lightning, than we have yet experienced, may chance to 

 attack us. For we are so far from knowing how great the magazine of light- 

 ning may be in the heavens, or in the earth, when it is ready to discharge itself, 

 either by one or more explosions, that we are ignorant even of the quantity actually 

 discharged, whenever any stroke of lightning visits us. Nor can the ablest 

 philosopher fix the limits of the greatest discharge that may possibly happen. 



Seeing then how vain it is to look for any thing like absolute security, in all 

 cases, it surely behoves us to proceed with caution. And it is for that reason I 

 have always considered pointed conductors as being unsafe, by their great 

 readiness to collect the lightning in too powerful a manner. And lest the con- 

 ductors, without such points, should be too slender for very violent attacks, in 

 places of great consequence, I have always recommended the having them above 

 4 times larger in diameter, than what are commonly made use of, that our 

 security may be the greater, by opening a larger passage for any extraordinary 

 discharge, and so far lessening the danger to be apprehended from it. 



I ought not, in this place, to omit taking notice of a paper, containing some 

 further experiments and observations, which were produced at the committee, to 

 show, among other things, that pointed metals were more disposed to receive 

 the lightning, by virtue of a repelling principle, in the lightning as well as the 

 electric fluid, which acted on the natural quantity of the fluid contained within 

 the metal, at a considerable distance from the point, causing, if I may be 

 allowed the expression, a kind of vacuum therein ; but I suppose the author 

 means to a certain distance only. 



So far from disputing this philosophy, I readily admit the fact. But, I am 

 afraid, every attempt to prove that pointed conductors may be so disposed to 



* Unless where tlie electrician, like Professor Richmann (who was killed by it) at his own hazard, 

 chuses to make further observations on lightning. — Orig. 

 VOL. XIII. 3 C 



