VOL. XLVII.] PHILOSOPHICAL TRANSACTIONS. 207 



When you force a hole through a piece of paper or pasteboard, attend to one 

 thing, which I constantly observe. If you electrize the plate of glass, ab, fig. 

 15, underneath, and that, by means of a thick iron wire somewhat bent, d, 

 you draw the spark through a piece of pasteboard, c, placed on the metal, with 

 which the glass is coated, the hole will appear invariably larger underneath, than 

 on the top of the pasteboard ; and this hole will have an impression at the place 

 where the iron wire shall have been supported. These 1 etFects leave no room 

 to doubt, but that the stroke of fire was directed from the glass to the conduc- 

 tor, E, by the bent iron wire. Besides, if the electric fire proceeds from the 

 upper surface of the glass, which receives the electricity from the under surface, 

 it necessarily follows, that it must have passed through the whole thickness of 

 the plate of glass ; and consequently that the glass is not impenetrable to the 

 electric fluid. 



The electrical experiments, which have been made here during the thunder, 

 are now sufficiently verified. Dr. le Monnier, assisted by his advantageous situ- 

 ation, has sufficiently experienced, first, that a bar of iron, pointed or not, is 

 electrized during a storm : 2dly, that a vertical or horizontal situation is equally 

 fitting for these experiments : 3dly, that even wood is electrized : 4thly, that by 

 these means a man may be sufficiently electrized to set fire to spirit of wine with 

 his finger, and repeat almost all the usual experiments of artificial electricity ; for 

 thus the Abbe denominates that which is excited by friction. 



Seeing therefore that these experiments succeeded so well, he attempted them 

 at Paris with a tube of tin, 18 feet in length, and of an inch and half in diame- 

 ter ; half of which tube he put out of the window, while the other half was placed 

 on, and fastened to, silk lines : and though he lived in the lowest part of Paris, 

 and his apartment in the Louvre is covered with an immense building, both in 

 height and extent, at any time when the thunder was but moderate, he per- 

 ceived signs of electricity. The sparks were more frequent after the lightning 

 than after the thunder ; and it even seemed that the clap of thunder put a stop, 

 for a very short time, to the force of the electricity. 



Mons. Cassini de Thury, who was desirous of observing these effects with the 

 apparatus which they had erected on the terrace of the observatory, made the 

 same remarks ; and he has had a greater opportunity of observing them, because 

 the effects there were more considerable, on account of the situation. He even 

 remarked very evident signs of electricity, though there was neither lightning 

 nor thunder, but only the sky covered with such thick clouds as seemed to fore- 

 bode a storm. 



Mons. le Roy, a member of the Academy of Sciences, who lives near the 

 Abbe, has repeated also a great number of these experiments and observations 



VOL. X. Q Q 



