37 
Franklin’s experiments were begun about the beginning of the year 1747, 
and seem to have been inspired by the receipt of a Leyden jar from a 
friend, Mr. Collinson, of London. He propounded the theory of positive 
and negative fluids, which has lately, in a modified form, been brought so 
prominently into notice by the writings of Lodge; and he made an investi- 
gation of the principle of the Leyden jar, but the most important of his 
researches relate to the identification of electricity and lightning. The 
probable identity of the two phenomena had been hinted at, as we have 
seen, by several observers, but Franklin went systematically to work to 
test the hypothesis. Under date November 7th. 1749, the following pas- 
sage is found in his note book: 
“Blectric fluid agrees with lightning in these particulars: (1) Giving 
light; (2) Color of light; (8) Crooked direction; (4) Swift motion; (5) Being 
conducted by metals: (6) Crack or noise in exploding: (7) Subsisting in 
water or ice; (8) Bending bodies in passing through; (9) Destroying ani- 
mals; (10) Melting metals; (11) Firing inflammable substances; (12) Sul- 
phurous smell. The electric fluid is attracted by points; we do not know 
whether this property is in lightning, but since they agree in all the partic- 
ulars wherein we can already compare them, is it not probable they agree 
likewise in this? Let the experiment be made.” 
The hypothesis was elaborated and sent to his friend Collinson, who 
communicated it to the Royal Society. This Society rather ridiculed Frank- 
lin’s idea at first, but his paper was published in London and also in 
France, and attracted considerable attention. 
The experiment was first made in France by M. d’Alibard, at Marle, 
on May 10th, 1752, and repeated shortly afterward by M. de Lor, in Paris. 
The results of what were called the Philadelphia experiments were com- 
municated to the Royal Society and caused quite a stir in scientific cir- 
cles. It is right to say with regard to the Royal Society, that Franklin’s 
Claims to scientific recognition were championed by Sir William Watson 
and were fully indorsed by the Society by Franklin’s election to fellow- 
ship and the award of the Copley Medal, together with the free donation 
of the Society’s transactions during his life. 
Franklin’s own experiments with kites are well known, as is also the 
method of protecting buildings from lightning, which was introduced by 
him and is still very widely used, although it has been greatly abused by 
the lightning-rod man. 
