704 Transactions of the American Institute. 



force, darting with such unparalleled velocity through it, that makes the 

 only noise that can be properly ascribed to the motion of the lightning. 

 The reverberation is but an echo of the explosive sound, returning, 

 as all echoes do, like for like. The idea that the prolonged, or any 

 sound of thunder, is caused by the collapse of the atmosphere, after 

 a partial vacuum produced by the passing of electricity tli rough it, 

 was never accepted as satisfactory, and it cannot be maintained by 

 any show of reason. The supposition of there being but a single report 

 for each volume of accumulated gases exploded, agrees with all the 

 facts and phenomena of lightning and thunder, as seen and heard, and 

 with the analogies of sounds proceeding from other causes, the explo- 

 sions of artillery or magazines for instance, which, when occurring in 

 hilly and mountainous regions, are followed by reverberations precisely 

 similar. 



If it be true that the prodigious quantities of electricity which are 

 visibly displayed in the thunder storm ascend thither from the earth, 

 and the loud thunder which shakes the firmament is the report of vast 

 explosions, then there must be in the clouds immense accumulations 

 of explosive gases ; the clouds must furnish, by the combined opera- 

 tion of heat and moisture, the source of those gases ; electricity the 

 agency by which they are produced, and lightning that which explodes 

 them. These facts- appear to afford very strong corroboratory testi- 

 mony in favor of the theory We have suggested in relation to the explo- 

 sion of steam boilers. Newton perceived in the fall of an apple the 

 principle of gravitation. Franklin saw in the zigzag course of the 

 electric spark and its crackling noise the identity of electricity with 

 lightning. How can we fail to recognize, in the numerous points of 

 resemblance between the phenomena of the thunder storm and the 

 facts of the boiler explosions, the identity of the causes which pro- 

 duce them all ? 



Recurring to the explosion of the steam boiler in Duke street, 

 Lancaster, there was no occasion to fancy any defect in the material 

 or construction of the boiler or deficiency of the water, or want of 

 skill or care on the part of the engineer, in despite of all the testi- 

 mony upon these points. On the hypothesis that volumes of the 

 gases accumulated in the boiler were exploded by an electric spark, 

 all that followed was a natural result ; instantly the building was lev- 

 eled to the ground and the ruins scattered with terrific violence, show- 

 ing that the force was exerted upon all points and in all directions. 

 Being an explosive force, it operated upon the parts affected by the 

 expansive pressure of the gases, which was equal on every side, for 



