39G MkccUmnes. 



part of the experiments were made in a south west cliamber, in 

 whicli the light was distributed upon the apparatus cfjually from all 

 sides. It was in no case exposed to the direct rays of the sun. 



His first experiments related to the oxidation of pnre iron by ter- 

 restrial magnetism. It was found necessary to use extreme precau- 

 tion in choosing the iron on account of tlie great inequality observa- 

 ble in its texture. The best chosen wires are far from being homo- 

 geneous. Among ten pieces, a few inches long, cut from the same 

 wire, and which appeared identical, not one was found, which, in an 

 acid, was attached equally in all its points. In some of his first trials, 

 the northern end appeared more oxidized, but he recollected, that 

 lie had handled them with naked hands, and remarked that the light 

 fell upon them unequally* 'After using every precaution, the result 

 of thirteen experiments is 



L On oxidation. 



1st. That the oxidation of iron placed under water is not influ- 

 enced by terrestrial magnetism. There Is no point in the horizon 

 toward which it is placed, which produces either a stronger or a 



more prompt effect. 



2nd. The oxidation which proceeds from tlie unequal texture of 

 the iron, always begins at the points in which the Iron is in contact 

 willi some other body, not only metallic, but with wax or carthern 

 ware. 



3rd. Diffused light, or weak solar rays neither hasten nor retard 

 oxidation, when the heat accompanying it is insensible, as is the case 

 in a warm room in winter. 



II. Eleven experiments were made to ascertain whether magnet- 

 ic needles would be acted on in water or in acids differently from 

 needles unmagnetized, and the result presents nothing whatever 

 favorable to the opinion of there being any difference In the oxida- 

 blillty of the two poles of a magnet. They confirm what had been 

 observed witli regard to the contact of foreign bodies. 



Ill* Fifteen experiments were cautiously made to determine wheth- 

 er terrestrial magnetism had any influence in the crystallization of ni- 

 trate of silver or formation of the Arbor Dianae by means of mercu- 

 ry in a syphon tube ; and others, with respect to the precipitation 

 by Zinc, of acetate of Lead. In none of these cases was it found that 

 terrestrial magnetism bad any effect whatever. Neither the position 

 of the tube, nor even diffused light, appeared to hasten or retard the 



crystalli/Btion. 



