126 Astronomical and Nautical Collections. 



with chalk and a piece of lime-tree wood, so as to form on 

 it shining zones, about two or three lines in length. The 

 steel, thus prepared, being exposed in a place strongly- 

 enlightened by the sun, was found, after some time, to 

 become strongly magnetic in the way that has been de- 

 scribed. The time, other things being equal, seemed to 

 depend on the intensity of the solar light ; for when I con- 

 centrated the light, by means of a lens, on the polished 

 parts, I obtained as strong a magnetism in a few minutes, as 

 was produced by an exposure of several hours to the light 

 in its natural state. 



A piece of steel, merely polished at one of its extremities, 

 receives a north pole at that end, and a south pole at the 

 other. If the polished part is in the middle, the two ex- 

 tremities become south poles, and the middle a north pole. 

 If the wire, on the contrary, is polished at the two ends, 

 they become north poles, while the middle is a south pole. 

 Lastly, if there are several polished zones, each of them 

 receives the boreal magnetism, and the dark zones which 

 separate them, the austral. In this manner we may obtain 

 an unlimited number of magnetic poles, provided that the 

 steel wire be of a length proportional to it. I have thus 

 easily procured eight poles, in a wire eight inches long, 

 although of unequal force : for I have constantly found that 

 the poles at the ends were stronger than the rest, and that 

 they preserved their magnetism for a longer time. I have 

 not been able to magnetize by the same means wires, either 

 entirely covered with oxyd, or perfectly polished, nor other 

 wires with longitudinal polished stripes. 



The whole of these results were the same, whatever might 

 be the position of the wire with respect to the meridian ; 

 and each experiment was repeated several times without any 

 variation in its success. It is unnecessary to add, that be- 

 fore each wire was exposed to the sun's rays, I carefully 

 examined whether or no it was magnetic, and those wires 

 which possessed any magnetic properties were rejected as 

 unfit for the experiment. 



