122 Mr. Murrafs Reply to B. M. [Feb, 



should we fall in the contest, but it is neither expedient nor pro- 

 fitable to exchange " thrusts " with a shadow. I have thus 

 premised, because I have laid it down as a fixed principle never 

 to notice any attack upon me by anonymous personages, and 

 this must be my apology for the undisturbed silence 1 shall in 

 future preserve in similar cases. 



The observations introduced into the pages of the Philoso- 

 phical Magazine comprise only a veri/ few selected from very 

 matii/ experiments on the subject in question, and I drew my 

 inferences from the combined aggregate, and not from individual 

 and insulated phaenomena. The inejficaci/ of steel or iron filings 

 in cases of poisoning by muriate of mercury as pronounced by 

 B. M. and their efficacy as inferred by analogy, on my part, is 

 the subject in both cases of mere opinion. Here then we stand 

 on equal ground. The subject of poisons has received much of 

 my attention ; and when my experiments come to be detailed, 

 perhaps it will be seen that I shall have laboured to better pur- 

 pose in this interesting field than B. M. 



This writer has inferred, that the steel he used had no magne- 

 tism in its composition, because it did 7iot attract ironjilings ; 

 but how numerous are the instances where magnetism obtains, 

 and this property is absent. De la Rive's floating annulus is 

 highly magnetic, but I have not observed any tendency to attract 

 iron fiHngs. Perhaps the authority of Sir H. Davy may weigh 

 with B. M. " The only proof of the magnetic powers of electri- 

 city passing through such a fluid was afforded by its effect upon 

 the magnetized needle." But it is needless to extend observa- 

 tions of this description, when we know position, juxta position 

 with a magnet, filing, hammering, scowering, twisting, &c. all 

 communicate magnetism to steel or iron ; and it is more than 

 probable that magnetism is never absent from iron, and that to 

 this may be ascribed the action of ferruginous bodies on the 

 magnet in which the attractive effect seems mutual. 



1 was not ignorant of the action of muriate of mercury or 

 nitrate of silver on steel which B. M. has presumed to suppose 

 (after //e himself seems to have been set right with respect to the 

 latter) by referring to the authorities he thus superfluously 

 quotes. 



The precipitation of one metal by another, as of copper by 

 iron, silver by copper, &c. has been ascribed to voltaic influence 

 by Von Grotthus, Sylvester, Donovan, Sec; while the principle 

 is generally recognized by philosophers ; and, prima facie, is it 

 not reasonable to suppose that the separation of every metal 

 from its combination with every acid whatever (at least to the 

 great extent 1 have proved it to be) is to be attributed to the 

 magnetism of the iron or steel, an influence or power possessed 

 almost exclusively by them ' Where am I to find recorded that 

 iron separates silver from a solution of the acetate, or platinum 

 from the nitromuriate, &c. Even the extensive and almost 



