ON THE METALS OF EARTHS. 99 



because the condition to which chemical effects are owing is 

 wanting in it, as I have explained in my former paper; hvi%. 

 the size of the plates influences the frequency of the strikin^s 

 of the little electmscopic pewdw/a, when their simple diver- 

 gence is exceeded; because each time that one of them 

 strikes, either at the negative or the positive side, that in- 

 stantaneous communication of the column with the ground 

 changes in some degree its electric state ; and the same state 

 is sooner restored, to produce another striking, in propor- 

 tion to the size of the plates, with the same number of groups. 

 This effect will enter as an essential circumstance into the 

 lid part of this paper, concerning the aerial electroscope. 



II. 



The Baker lan Lecture for I8O9. On some new Electro-* 

 chemical Researches, on various Objects, particularly the 

 metallic Bodies from the Alkalis, and Earths, and on 

 some Combinations of Hidrogen, By Humphry Davy, 

 Esq. Sec. R. S. F. R. S. E. M. R. LA. 



( Concluded from p. 55. J 



IV. On the Metals of Earths, 



JL HAVE tried a number of experiments, with the hopes Metals of the 

 of gaining the same distinct evidences of the decomposition coni™on 

 of the common earths, as those afforded by the electro- 

 chemical processes on the alkalis, and the alkaline earths. 



I find, that, when iron wire ignited to whiteness, by the apparently 

 power of 1000 double plates, is negatively electrified and combined witlii 

 „,. 11 1 1- I- iron, 



fused in contact with either silex, aiumine, or gluc^ne, 



slightly moistened and placed in hidrogen gas; ■■ e iron be- 

 comes brittle and whiter, and affords by solution in acids an 

 earth of the same kind, as that which has been employed in 

 the experiment. 



1 have passed potassium in vapour through each of these potassium ia 

 earths, heated to whiteness in a platina tube : the results vapour 

 were remarkable, and perhaps not unwgrthy of being fully 

 detailed. 



H 2 When 



