THE DEVELOPMENT OF ELECTRICAL SCIENCE. 219 



tive fluids, which has lately, in a modified form, been brought so 

 prominently into notice again by the writings of Lodge, and he made 

 an investigation 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 of November 

 7, 1749, the following passage is found in his notebook: "Electric fluid 

 agrees with lightning in these particulars : (1) Giving light; (2) color 

 of the light; (3) crooked direction ; (4) swift motion; (5) being conducted 

 by metals; (6) crack or noise in exploding; (7) subsisting in water or 

 ice; (8) rending bodies in passing through; (9) destroying animals; (10) 

 melting metals; (11) firing inflammable substances; (12) sulphurous 

 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 

 particulars wherein we can already compare them, is it not probable 

 that they agree likewise in this 1 ? Let the experiment be made." The 

 hypothesis was elaborated and sent to his friend Collinson, who com- 

 municated it to the Eoyal Society. This society rather ridiculed 

 Franklin's ideas 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 Marli, 

 on May 10, 1752, and it was repeated shortly afterwards by M. de Lor 

 in Paris. The results of what were called the Philadelphia experiments 

 were communicated to the Royal Society and caused quite a stir in 

 scientific circles. 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 his election 

 to a fellowship 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. 



During the next decade Canton discovered the now commonly known 

 difference between vitreous and resinous electricity. Beccaria experi- 

 mented on the conducting power of water. Symmer made a number of 

 interesting experiments on the electrification of different kinds of 

 fabrics by friction and propounded a theory of two electric fluids. 

 Contemporaneous with these were a number of other experimenters 

 who added to the stock of knowledge of this class of phenomena. 



The experiments of iEpinus and others on the pyroelectric proper- 

 ties of tourmaline now began to attract attention. The experiments 

 of the Abbe Haiiy are perhaps the most important in this connection 

 at this stage of the subject. He found the polar properties of the 

 crystal and showed that similar properties were possessed by a number 



