Exptriment luUh an Artificial Thunder-Cloud. 



CASE I. 



437 



THE elearicity oppofite to that of the cloud, that is, the lower furface of the body of 

 charged air, is fuppofed to extend over the condudor, and over all metallic fubftances be- 

 longing to the building. 



The conduftor is therefore connedled with the communication between the interior cy- 

 linders i and one of the infulated balls being connefted by means of the glafs tube with the 

 conductor, let the other ball be connedled with the interior cylinders. 



RESULT. 



WHEN the condudtor was terminated by a point, and the cloud pafled near it, an explo- 

 fion took place upon the point, and the eledrified air between the cylinders was inftantly dif- 

 charged. When the cloud pafled at a greater diftance, no explofion took place ; but the 

 eledtricity difappeared from the-tinfoiled cylinders, and the plate of air between them was 

 filently difcharged, as was fliewn by the eleflrpmeter. 



When the condu£lor was terminated by a ball, and the cloud pafled near it ; the ball was 

 ftruck, and the plate of air between the cylinders difcharged as before : but when the cloud 

 pafled beyond the firiiing dijiance to the ball, the tinfoiled cylinders continued ele£trified, as 

 was (hewn by the eleftrometer ; and the plate of air remained in a charged flate. 



Jn this cafe no fparks pafled between the balls where the rofin was placed. 



CASE II. 



THE lower furface of the body of charged air is now fuppofed to extend over fome of the 

 metallic fubftances belonging to the building, but not over the condudor. 



The communication between the conduftor and the interior cylinders being removed, the 

 remainder of the apparatus was arranged as in the firft cafe. 



RESULT. 



WHEN the condu£lor was terminated by a point, and the cloud pafled near to it -, a fpark 

 took place on the point, and the rofin in the interval between the balls was inftantly fet on 

 fire. When the cloud pafled at a greater diftance, the cleftricity of the charged air difap- 

 peared filently, as in the firft cafe. 



When the condu£lor terminated by a ball, and the cloud pafled near to it ; it was ftruck 

 and the rofin between the balls inftantly fet on fire : but when no fpark pafled between the 

 cloud and the ball, no fparks pafled where the rofin was placed, and no decreafe of elec- 

 tricity appeared upon the tinfoiled cylinders. 



CASE III. 

 THE lower furface of the body of elcftrificd air is now fuppofed not to extend over any 

 part of tlie building, and confcqiiently not over the conduftor, or over any other metallic 

 fubftancc belonging to it. 



3 Thw. 



