ON THE EtECTKIC COLUMN. g5 J 



tween the increase of the quantity of electric jiuid and the 

 (Jirainution of that of aqueous vapour in the atmosphere, 

 tluring this period. 



Art. IX. This points out, in the first place, ^formation The electric 

 oi electric Jiuid in the atmosphere, while the suvls rays per- ^V'^ increase* 

 vade it. Light, the increase of which in the atmosphere is sence of the 

 here the immediate cause, is certainly one of the component ^"°* 

 parts of the electric fiuid ; therefore, \.\\\s fluid must be com^ 

 posed m some operation of nature on our globe. Now it is 

 here already probable, that the sun's rays, in pervading the 

 atmosphere, encounter in it the substances with which they 

 compose the new quantity of electric fluid then manifefted : 

 and that, in general, they enter there into various combina- 

 tions, is proved by their intensity being sensibly greater on The solar ray* 



the top of high mountains than in the lower parts of the at- ^°[^ intense 



r o r^ on heights. 



mosphere, as has been shown from experiments by Mr. de 



Saussure; which difference must proceed from their quan- 

 tity being diminished in pervading the air. 



Art. X. #ome other experiments of Mr. de Saussure lead Farther in- 

 besides directly to this system concerning compositions and ^a^^'^f^ f .h 

 decompositions oi electric fluid, as producing phenomena, com losition 



the causes of which were unknown or mistaken. For ix)_ and decornpo- 



sition of the 

 stance, it has been found by experience, that, when water is elecuic fluid. 



poured upon an insulated plate of hot iron connected with 

 an electroscope, this plate becomes negative: whence it had 

 been concluded, that, when water is converted into vapour, 

 it acquires a greater capacity for electric fluid; and thus 

 deprives of a certain quantity of this fluid the body on 

 which it evaporates. But Mr. de Saussure, having repeated 

 the same process upon different heated bodies, found, that 

 some, in particular silver, became po^i/fye .- whence he con- 

 cluded very naturally, that during the evaporation of water 

 on hot iron some electric fluid was decomposed, and some on 

 the contrary composed when the same operation took place 

 on silver. He has also surmised, what I have since found 

 by direct experiments related in my work Idees sur la Mc" 

 teorologie, that in the discharge of the Ley den vial, and m 

 my experiments of the magic picture, the spark produces 

 some diminution of the quantity of electric fluid on these 

 bodies ; which cannot be but by decomposition. It will suc<^ 



oessively 



