638 PHILOSOPHICAL TRANSACTIONS. [aNNO 1734. 



in relating the historical proofs of his hypothesis concerning the nortiiern lights, 

 taken from the records we have of several appearances of those lights, to be 

 met with in ancient authors, compared with those of the zodiacal light, their 

 supposed cause, and the situation of the earth in her annual orbit at those 

 times. The last section consists of 28 curious questions, concerning several 

 other phaenomena of nature, which the ingenious theorist believes to have a 

 dependance on his new hypothesis, and explicable by it. 



The cause of an aurora borealis, in general, the author takes to be a light 

 called the zodiacal light, which is in reality nothing else but the atmosphere of 

 the sun, spread on each side of him along the zodiac, in the form of a pyramid. 

 This sometimes is extended to such a length as to reach beyond the annual or- 

 bit of our earth, and in these circumstances soinetimes to blend itself with our at- 

 mosphere, and being of an heterogeneous nature, produces the several appear- 

 ances which are observed in, and usually compose the northern lights. This he 

 undertakes to explain, and prove more largely, in the sequel of the work. 



On Eleclricity. By Mons. Du Fay* F. R. S. N° 431, p. 258. 



The writings of Mr. Gray and Mr, Hauksbee, it seems first put M. Du Fay 

 on the subject of electricity, and furnished him with the hints that led to the 

 following discoveries. 



1. He found, that all bodies, (metallic, soft, or fluid ones excepted) may be 

 made electric, by first heating them more or less, and then rubbing them on 

 any sort of cloth. So that all kinds of stones, as well precious as common, all 

 sorts of wood, and in general every thing that he tried became electric, by heat- 

 ing and rubbing, except such bodies as grow soft by heat, as the gums, which 

 dissolve in water, glue, and such other substances. It is also to be remarked, 

 that the hardest stones and marbles require more chafing or heating than others, 

 and that the same rule obtains with regard to the woods ; so that box, lignum 

 vitae, &c. must be chafed almost to the degree of burning ; whereas fir, lime- 

 tree, and cork, require but a moderate heat. 



•1. Having read, in one of Mr. Gray's Letters, Phil. Trans. N" 422, that 

 water may be made electrical, by holding the excited glass tube near it, M. Du 

 Fay found on trial, that the same happened to all bodies without exception, 

 whether solid or fluid; and that for that purpose it was sufficient to set them on 

 a glass-stand slightly warmed, or only dried ; and then by bringing the tube 



* M. du Fay was a French officer ; but after some years service, he quitted the army and devoted 

 himself wholly to scientific pursuits. He was an active member of the Parisian Acad, of Sciences, 

 aud had the superintendance of the Royal Botanic Garden at Paris. He died of the small-pox in 

 the 43d or 44th year of his age. His life is in tlie collection of Eloges by Fontenelle. 



