BOOK III. CHAP. VII. 6j9 



If tlie communication be through tlie air without .my coiidudor, 

 a bright hglit is feen between the bodies, and a found is heard. In 

 the eledrical experiments, this hght and found is called the electric 

 fpark and fn ap ; but in the great operations of nature, it is called 

 lightning and thunder. — If the communication of this fluid is by a 

 condu£tor, it may be without either light or found, tiie fubtile fluid 

 pafling in the fubftance of the condutftor, 



IF the coaduftor be good and of fuflicient bignefs, the fluid paffes 

 through without hurting it ; if otherwife, it is damaged or deftroyed. 

 All metals arid water are good conduclors. Other bodies may be- 

 come condudors by having fome quantity of water in them, as wood, 

 and other materials uled in building ; but, not having much water 

 in them, they are not good ' condudors, and therefore are often 

 damaged. — Glafs, wax, refui, filk, wool, hair, feathers, and even wood 

 perfedly dry, are non-condudors ; that is, they refill inftcad of fa- 

 cilitating the pafluge of this fluid. 



When this fluid has an opportunity of pafling through two con- 

 dudors, one good and fufficient, as of metal, the other not fo good, 

 it pafles in the beft, and will follow it in any diredion. — The clouds 

 have often more of this fluid in proportion than the earth ; in which 

 cafe, as foon as they come near enough for within the fl:riking dif- 

 tance), or meet with a condudor, the fluiJ quits them and flirikes into 

 the earth. A cloud fully charged with this fluid, if fo high as to be 

 beyond the ftriking diftance of the earth, paffes quietly without mak- 

 ing noife, or giving light, unlcfs it meets with other clouds that 

 have lels. — Tall trees and lofty buildings, as the towers and fpires 

 of churches, become fomctimcs condudors between the clouds and 

 the earth ; but, not being good ones, th;,t is, not conveying the fluid 

 freely, they are often damaged. 



Buildings that have their roofs covered with lead, or other metal, 

 and Ipouts of metal continued from the roof into the ground, to 

 carry off the water, are never hurt by lightning ; as, whenever it falls 

 on fuch a building, it paiies in the metals, and not in the walls. — 

 When other buildings happen to be within the flriking diftance from 

 luch clouds, the fluid pafles iu the walls, whether of wood, brick, 

 or ftone, quitting the walls only when it can find better condudors 

 near them ; as metal rods, bolts, and hinges of windows and doors, 

 gildings on wauilcot, or on frames of pidures ; the filvering on tiic 

 backs of looking glafies, the wires for bels, and the bodies of ani- 

 mals as containing watery fluids. And, in palling through the houle, 

 it follows the diredion of thele conductors, taking as many in its way 

 as can allift its paiTage, whether in a llraight or crooked line; leap- ■ 



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