3 5 2 Conductors fo preferring Buildings. [Book IV. 



out the little piece of wood to a confiderable diftance, 

 by the natural force of the explofion. 



Unfcrew the ball, and let the point which is under- 

 neath be prefented to the conductor, and then you will 

 not be able to charge the jarj for the fharp point 

 draws the fire filendy from the conductor, and conveys 

 it to the coating on the outfide of the jar. 



The prime conductor in this experiment is fup- 

 pofed to reprefent a thunder cloud difcharging its con- 

 tents on a weather-cock, or any other metal, at the 

 top of a building; and it may be inferred from this 

 experiment, that if there is a connection of metal to 

 conduct the electric fluid down to the earth, the 

 building will receive no damage j but where the con- 

 nection is imperfect, it will ftrike from one part to 

 another, and thus endanger the whole building. 



Elevated conductors, applied to -buildings to fecure 

 them from lightning, will in this, manner difcharge the 

 electricity from a cloud that pafles over them, and a 

 greater quantity of the difcharge will pafs through a 

 pointed conductor, than through one which termi- 

 nates with a ball ; but whether the difcharge will be 

 made by a gradual current, or by explofion, will de- 

 pend upon the fuddennefs of the difcharge, on the 

 nearnefs and motion of the cloud, and the quantity of 

 the electricity contained in it. If a fmall cloud hangs 

 fufpended under a large one loaded with electric mat- 

 ter, pointed conductors on a building underneath will 

 receive the difcharge by explofion, in preference to 

 thofe terminated by balls, the fmall cloud forming an 

 interruption, which allows only an inftant of time for 

 the difcharge *. 



Vifcount Mahon (now Earl Stanhope) has com- 



* Mr. Adams's Effay on Eleft. p. 1 86. 



municated 



