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t * ~ t f) r '\ . /~S v i -r jir ' v v o r*r 
■ ? • * ' » I \ I T' i 'A ■ : '1 " | t 1J 
VI. J Letter from Stephen Gray, F. (^. S. to 
Dr. Mortimer, Seer . (2^. S\ containing fome 
Experiments relating to Ele&ricity. 
T H E following Lines contain an account of 
what Eledtrical Experiments I have made fince 
thole I laft communicated to the Society which 
was in February laft. 
February the 1 8th, I tried what Effed: would be 
produced on feveral Sorts of Wood with refpedt to 
the luminous Part of Eledricity : the Wood was 
made into Rods of the fame Form with thole Iron 
Ones mentioned in my former Letter upon this 
Subjed ; the Woods made ufe of were Fir, Alh and 
Holly, thefe being fuccellively difpofed upon Elec- 
trick Bodies, after the fame manner as the Iron Rods 
had been , the Tube being applied to one End, there 
appeared a Light on it, but not with lo great a 
Force, nor did the Light extend to fo great a length ; 
neither was the Form of it Conical, but rather Cy- 
lindrical i but the Extremity of it feemed to confift 
of a fhort Fringe of Light ; when the Light, that was 
given to the Rod by the application of the Tube, 
did ceafe, upon a motion of my Hand towards the 
Point of the Rod, the Light came out again, as has 
been mentioned of the Iron Rods ; but when the 
Hand or Finger was held near the Point of thele 
wooden Rods, there was no pricking or pufhing of 
the Finger felt, as when the IronRods were made ufe 
of I had fome of thefe Rods made much bigger at one 
End than the other, and now applying my Finger 
^to 
i 
