252 On the variaile Acl'ion of the Electric Column. 



and tliat they cannot be ojjposcd to my experiments made m 

 open air, u-hich demonstrate that the action of the column is 

 increased bv the increase of morslure, and diminished by dry- 

 nesf. But a more direct proof of it is related in the same Phi- 

 losophical Journal of Mr. Nicholson, for August ISIO, by some 

 experiments which I have made with my late very ingenious 

 friend Dr. Lind, for ascertaining immediately the influence of 

 moislvre on tlie action of the column. 



Ill this experiment all the parts of a column were first sepa- 

 rately laid on the heartli of a chimney before a great fire, so that 

 the pieces oi paper were almost singed. In that state we momited 

 the column, and it did not affect the gold-leaf electrometer. 

 We then dismoimtcd again tliat cohimn, and laid also the se- 

 parate pieces on a table in mv room, in which the hygrometer 

 was above 40°. When thcv had thus remained one hour, we re- 

 mounted tlie column, and it acted on the gold-leaves as it did 

 before the papers had been so thoroughly dried by a great heat. 



This I think to be a direct fact proving that a certain degree 

 o{ 7noisti/?-e in the column is indispensable for its conductive fa- 

 culty, the source of all its effects. I have found in all my ob- 

 servations, that '.vithin certain limits an increase of moisture in- 

 creases the action of the column ; but, whereas the effect of the 

 increase of heat is immediately perceived, as it easily ]ienetrates 

 the column, that of the increase of moisture is very slow, be- 

 cause, beginning at the edge of the papers on the outside, it 

 very slowlv propagates in the internal parts of the column ; a 

 circumstance of which Mr. ilonaids has not been aware, espe- 

 cially by his column being inclosed in a "las-, title. 



But the column being a very new apparatus, it requires some 

 time and a greater number of observers to follow all the views it 

 opens in the terrestrial plucnomena, especially in those of the 

 atnios])here \vhich constitute meteorology. This was my general 

 conelu.sion in a paper published in vohimexxxiii. of Mr. Nichol- 

 son's Philosophical .Tovirnal, under this title: " On Hygroloj^' 

 and Hygronietrv, and ti;eir Connexion with the Pl;a;nomena ob- 

 served in the Atniospiiere." There I 'demonstrated that im- 

 portant fact, not only in meteorology, but in natural philosophy, 

 that rain does not proceed from a quantity of aqueous vap07ir 

 or moisture existing at any time in any portion of the atmo- 

 sphere ; that it must proceed from the decomposition of the 

 atmospheric air itself, from which decomposition more or less 

 complete result all the meteors, lightnings, thunder, hail, and 

 other atmospheric api)earanccs. 



i have been thus particular in the examination of Mr. Ronalds's 

 ©pinions, as he has shown much ingenuity in his experiments, 



and 



