22S ZIGZAG MOTION OF THE ELECTRIC SPARK. 



Lateral prsss- As for the lateral pressure of air, when it experiences less 



me of a r on res i s t ance oa one s id e of its course than on the other, we 

 the sails of a . -, ■ . , . ' 



■:-,;. ;# have an example of this effect in the motions of ships ; why- 



do they change their course by the different inclination of 

 their sails ? It is because they offer less resistance to the 

 motion of the air, which thus changes its course ; however 

 it presses sidewise, so as to put the ship in a different motion, 

 which is determined by the rudder. This is an example ab- 

 solutely analogous, only inverse, of the change of course of 

 the electric spark ; this compresses the air, until finding less 

 resistance on one side, it suddenly changes its course. 

 Erroneous hy- I come to the author's hypothesis, in which he sets out 

 poihesjs. from this certain fact ; " that the electric fluid passes in a 



*' more direct line according to the best or the worst conduct- 

 " ing substances presented to it:" but not being sufficiently 

 ■ . conversant with meteorological phcenomena, he makes an 



hypothesis, which will give me the opportunity of showing 

 how necessary is their knowledge in every branch of experi- 

 mental philosophy, to avoid arbitrary, and even delusive hy- 

 % potheses. " Our atmosphere," he says, " being a compound 

 « of oxigen, &c. presents at once, to the spark, flying from 

 * e the machine, at least four known gasses ; all, / have not 

 ** the smallest doubt, differing in their conducting power, were 

 " they separately tried" This therefore remains a mere 

 hypothesis, till the trial has been made ; however he thus con- 

 tinues : *' This point being ascertained, the phenomenon is 

 " at once accounted for. The fluid flies to the next best con- 

 ** ductiug gas from a worse, as it would from different por- 

 " tions of matter." 

 Importance of I hope the author will see now, that he has not accounted 

 pieteoiological ^ r ^- g p] ienorn( -. non# But, Sir, he himself, or others of your 

 piiteaomeoa in ' ' ... 



science. readers, will I hope take some interest in a short account of 



the meterolog'ica! phenomena, which mi^ht have prevented 

 his hypothesis, in the first class of which are the following. 

 Nature of the ] have proved in my work Idees sur la Meteorohgie, — 

 1. That it is an errour to consider the principal mass of the 

 atmosphere as composed of two distinct fluids, or gasses, one 

 called oxigen, the other hidrogen; that atmospheric air is a 

 fluid sui generis, composed, in each particle, of all the ingre- 

 dients manifested in its decompositions. — 2 That atmospheric 



air 



