3 5 * Experiments relative [B ook IX. 



duced; he then brought the metals 'into contact with 

 each other, and, to his furprife, perceived a pale flam 

 of light diffufe itfelf over the whole of his eye. His 

 tongue was at the fame time affected with a fimilar 

 fenfation to that produced when both of the metals are 

 in contact with it. On darkening the room the flafti 

 became more diflinct and of a ftronger colour. If the 

 experiment is made with zinz and gold, inftead of tin- 

 foil and filver, the flam is incomparably more vivid. 

 By infmuating a rod of filver as far as poffible up the 

 ncfe and then bringing it into contact with a piece of 

 zinc placed upon his tongue, he alfo fucceeded in pro- 

 ducing the fenfation of a flam of light, rather more 

 vivid than when the filver was in contact with the ball 

 of the eye. Dr. Fowler alfo mentions that his friend, 

 Mr. George Hunter of York, difcovered that by 

 placing one of the metals as high up as poflible be- 

 tween the gums and the upper lip, and the other in a 

 fimilar fituation with regard to the under lip, a flafh 

 was produced as vivid as that occafioned by paffing 

 one of the metals up the nofe, and placing the other 

 upon the tongue. It differs, however, from the flam 

 produced in the other way, in the fingular circumftance 

 of not being confined to the eye alone, but appearing 

 diffufed over the whole face. On repeating the ex- 

 periment myfelf, and attending to the concomitant 

 fenfations produced by this difpofition of the metals, I 

 perceived that a fenfe of warmth, at the inftant that 

 they were -brought into contact, diffufed itfelf over the 

 whole upper furface of the tongue, proceeding from its 

 root to the point. Dr. Rutherford, to whom Mr. 

 Hunter had communicated this experiment, remarked, 

 on repeating it, that a flam is produced not only at the 

 inftant the metals are brought into contact, but like- 

 wife at the inftant of their feparation i while they re- 

 main 



