BOOK OF NATURE LAID OPEN. 179 



are infinite as its extent. Since the phenomena pro- 

 duced by this fluid have been observed with atten- 

 tion, the true cause of thunder and lightning seems 

 to be ascertained. As the motion of light is almost 

 instantaneous, and that of sound is at the rate of a 

 league in forty pulsations, the distance of thunder 

 may be easily ascertained; for, if we can count thir- 

 teen pulsations between the flash and the sound, the 

 thunder will be about a mile off. A means, how- 

 ever, has been invented, by which houses, ships, and 

 other buildings, may be secured from its ravages, 

 and places of the greatest safety, in thunder storms, 

 pointed out; but what are the evils experienced from 

 thunder storms, when put in competition with the ad- 

 vantages to be derived from them? What would 

 the atmosphere, it may be observed, become, but for 

 the winds? But, notwithstanding the blessings de- 

 rived from those wholesome ventilations, what would 

 become of the atmosphere itself, were it not for the 

 loud-roaring thunder, the forked lightning, and all 

 the other varieties of electrical phenomena, which 

 purge the air of those noxious substances that are con- 

 tinually mixing with it, and purify, by fire, the upper 

 regions, where so many light, inflammatory sub- 

 stances, are arrested .in their course? 



There appears to be a continual circulation going 

 on in the atmosphere, by which the inflammable air, 

 generated between the tropics, is made to ascend, by 

 its lightness, to the upper regions, where, by the mo- 

 tion of the earth, it is urged to the poles ; hence, the 

 inflammatory exhalations continually arriving and 



