314 Scientific Intelligence. [April, 



The composition of the conchoidal chloropal is : 



Silica 460 



Oxide of iron 35 '3 



Magnesia 20 



Alumina 10 



Potash and manganese Traces 



Water 1S-0 



1000 

 The earthy chloropal contains : 



Silica 450 



Oxide of iron 320 



Magnesia 20 



Alumina 0-75 



Potash and manganese Traces 



Water 20-0 



99 75 



Experiments were made to discover fluoric acid, sulphuric acid, 

 lime, and potash, but none was found. 



VIII. On the Galvanic Ignition of Charcoal. By Mr. W. West. 



(To the Editor of the Annals of Philosophy.) 

 SIR, Lved.~, Feb. \&W. 



In the Annals of Philosophy for Aug. 1822, there appeared a com- 

 munication from Dr. Hare, of Philadelphia, to the Editor, containing 

 an account of various interesting phenomena produced by means of 

 his galvanic deflagrator : one of these is the ignition of charcoal. 



Dr. Silliman, in a letter quoted in the above communication, after 

 describing the appearance of the charcoal at tl>e respective poles, the 

 cone and deposit at the positive, the concavity at the negative, goes on 

 to state as a discovery his having observed these appearances, and 

 adds, " I deem it indispensable that the experiments be performed 

 with the deflagrator." 



About twelve months since, when exhibiting the ignition of char- 

 coal before the members of the Philosophical Society here, I was 

 Struck with ihe eifect on the charcoal being so opposite at the two 

 poles; the crater on the negative side being well defined, and about 

 one-eighth of an inch deep, the cone on the positive charcoal corres- 

 ponding, and having at its apex a filament which continued lengthen- 

 ing until broken off by its own weight. I pointed out this in my lec- 

 ture, but though, as far as I recollect, it had not then been mentioned 

 in any work, I imagined all who had observed the ignition of charcoal 

 with a powerful battery must have seen the same effects produced. I 

 have since repeated the experiment several times, and have verified 

 most of the particulars mentioned by Dr. Silliman; I think that the 

 "vapour arising from the charcoal is more abundant when the ignition 

 takes place in vacuo than when in the atmosphere. 



I wish to observe more accurately than Dr. Silliman appears to have 

 done, whether there be an increase of weight after ignition in the char- 

 coal at the positive pole ; but having little prospect of leisure at pre- 



