136 THUNDER Sc LIGHTNING. [Lesson XXII. 



POWER which produces such stupendous effects, 

 will be naturally led to inquire by what natural 

 means they are occasioned. 



An opinion very prevalent among philosophers 

 until late years, was, that this awful class of 

 phsenomena is produced by a variety of acetous, 

 bituminous, spirituous, nitrous, and sulphureous 

 particles, exhaled from various bodies, and raised 

 into the air; and there being driven to and fro by 

 the wind and other causes, are at length violently 

 agitated, and furiously striking against each other 

 force themselves through the clouds, attended with 

 an explosion which we call Thunder, and a flame 

 or flash which is called Lightning: the bituminous 

 and sulphureous particles causing the flash, and 

 the nitrous particles occasioning the explosion. 



But it is now universally allowed, that Thun- 

 der-storms are produced by electricity : the proof 

 of this was reserved for Dr. Franklin, who is 

 so justly celebrated for his many discoveries 

 particularly in that branch of natural philosophy 

 which was the subject of the preceding Lesson. 

 This philosopher traced out with much accuracy 

 several particulars in which Lightning and the 

 Electric Spark agree : a few of these I shall here 

 mention. 



Flashes of L'ghtning are generally seen crooked 

 and waving in the air: this is also the case with the 

 Electric Spark, when it is draun from an irregular 

 body at some distance. Lightning strikes the 

 highest and most pointed objects in its way, pre- 

 ferably to others: in like manner, all pointed con- 

 ductors 





