Dr. Schunck on Rubian and its Products of Decomposition. 213 



train ; it is as active as the positive wire ; it collects round it a 

 whole class of bodies with as much energy as the positive wire 

 does an opposite class ; how then are we to understand its absence 

 in the deflections obtained by Faraday with common electricity 

 in the experiment described? If we look upon the influence 

 acting in two indispensable poles as the cause of voltaic pheno- 

 mena, can we consider phenomena produced by one pole as 

 emanating from the same cause ? 



For my own part, I cannot dismiss from my mind a strong 

 impression that the agent in Faraday's experiment was not the 

 same as that which causes voltaic phsenomena. Nay, more than 

 this, if it be proved by his experiment that common electricity 

 does not require a twofold polar arrangement in order to produce 

 deflections, I cannot see what the use is of the two poles used in 

 his and Colladon's experiments with the Leyden battery; one 

 of them must have been superfluous. If this be so, we arrive at 

 this general proposition, that voltaic electricity is composed of 

 elements existing in such ratio, and so combined and modified, 

 that it must be brought to bear upon the subject of its action by 

 means of two poles simultaneously and equally energetic; while 

 the proportions and mode of combination in the common electric 

 fluid are such that it produces the same effect with one pole only. 

 Thus, by Faraday's experiments, if my reasonings be correct, an 

 important difference is established, instead of an identity ; other 

 facts and arguments of the same tendency will be hereafter 

 brought forward. 



I now take leave of this part of the subject, and proceed to 

 consider some other evidences which have been brought forward 

 in support of the affirmed efficiency of quantity to explain the 

 differences observable between the effects of common and voltaic 

 electricity. It is a subject deserving full consideration, as on 

 this foundation is raised the whole superstructure. 

 [To be continued.] 



XXXII. On Rubian and its Products of Decomposition. 

 By Edward Schunck, F.R.S.* 



Part 1. 



AMONG the many discussions to which the subject of madder 

 lias given rise among chemists, there is none which is caL 

 Ciliated lo excite so much interest as that concerning the state 

 in which the colouring matter originally exists in this root, and 

 there is no part of this extensive subject which is at the same 



* Prom tin- Philosophical Transactions for 1851, part ii. ; having been 

 received by the Royal Society January D, and read February 13, 1851. 



