DISCO VEKY BY MEANS OF NEW OBSERVATIONS. 567 



above this the decrease again continued at the same rate 

 as before. It was by observing a fume, on scratching a 

 piece of electro-deposited antimony, that I was led to 

 discover the singular heating property of that substance. 



Otto Gruericke was the first to discover by observation 

 that electrified sulphur first attracted and then repelled 

 a feather, and that substances charged with the same kind 

 of electricity repel each other, also that light bodies 

 within the sphere of electrical influence become electri- 

 cally excited. Sparks were first recorded by Wall in the 

 year 1708, as having been observed whilst rubbing amber. 

 Dr. Miles, in the year 1745, first observed the pencil of 

 luminous rays which issue from an electrified point. In 

 the same year, Dr. Watson discovered by observation, that 

 on electrifying large bodies by induction, the parts of 

 them which are most distant from the electrically excited 

 body had electricity developed in them. Du Fay and the 

 Abbe Nollet, first observed that sparks might be drawn 

 from the living human body ; and the latter said : ' I 

 shall never forget the surprise which the first electric 

 spark ever drawn from the human body excited both in 

 M. Du Fay and myself.' This was the origin of the 

 electric kiss, &c. It was by observation also, that the 

 Abbe Nollet, in 1746, discovered that electricity increases 

 the rapidity of flow of liquids from minute orifices. 

 Franklin observed, that when the inside of a Leyden jar 

 was electrified positively, its outside was electrically 

 negative, and that the electric shock was produced by 

 the restoration of electrical equilibrium, when the inner 

 and outer surfaces were connected together. It was by 

 means of observation, that Symmer, in the year 1759, 

 discovered that the two electricities were not independent 

 of each other, and that the one could not be set free with- 

 out the other. In 1791, Haiiy discovered by observation, 



