ACTION OF WATER ON IRON. 2^9 



brewery in Dublin*, where it was supposed to have lain in about 

 20 feet of water for nearly eleven years. 



The bar lay approximately due north and south, horizontally. 

 When taken up it was found powerfully magnetic, with polarityj 

 and though the bar was throughout equally exposed, corrosion 

 had alone taken place at its two extremities. The ends were 

 injudiciously cut off, by which its magnetism was almost de- 

 stroyed. This curious subject needs further elucidation. It is 

 doubtful if any authentic instance has yet been given in which 

 magnetism appeared directly to play a chemical part. And the 

 question is one of considerable importance as regards our sub- 

 ject ; for, as it is well known that bars of iron, by long standing 

 in the vertical or certain other positions, acquire magnetic pro- 

 perties ; if it should be found that magnetic polarity exercises 

 any direct effect upon chemical agencies, then it may result 

 that the duration of a structure in iron may in some degree de- 

 pend upon the position of its parts with respect to the magnetic 

 poles of the earth. 



Long since. Professor Maschmann, of Christiana, published 

 some curious experiments, which were confirmed by Hansteen, 

 on the effects of a magnet on the crystallization of the Arbor 

 Dianfe, in a U-shaped tube of glass, beneath or above which it 

 was placed. (Quarterly Journal of Science, vol. xvii. p. 158.) 

 His results, howevei', were denied by some British chemists at 

 the time. 



66. Since that time, the investigation of this influence, which 

 has been repeatedly asserted and denied, has been undertaken in 

 a very careful and particular manner by Professor Erdmann. 

 He first points out the number of delicate perturbing causes 

 which may, and have occasionally led to mistakes, pointing out 

 the effects produced by irregularity in the wires, handling them 

 with the uncovered fingers, &c. &c.; and especially states that 

 many repetitions of each experiment should be made. The bars 

 and magnets which he had occasion to use were very powerful, 

 some of them competent to lift 80 pounds. 



I. By experiments made to ascertain the oxidation of the 

 iron wire, when under the influence of terrestrial magnetism, it 

 was ultimately proved, — 1st. That the oxidation of iron placed 

 under water is not at all influenced by terrestrial magnetism. 

 There is no point of the horizon towards which it is more 

 strongly or more quickly produced than towards another. 2nd. 

 The oxidation arising from imequal contexture of the iron 

 always begins at the point where the wire is in contact tvith 



* Messrs. Guinness, James' Gate, 

 T 2 



