366 FRAGMENTS OF SCIENCE 



them; or get a smith to cut a length of ten inches from 

 a bar of steel an inch wide and half an inch thick; file 

 its ends smoothly, harden it, and get somebody like my- 

 self to magnetize it. Procure some darning needles, and 

 also a little unspun silk, which will give you a suspend- 

 ing fibre void of torsion. Make a little loop of paper, or 

 of wire, and attach your fibre to it. Do it neatly. In the 

 loop place a darning-needle, and bring the two ends or 

 poles, as they are called, of your bar-magnet successively 

 up to the ends of the needle. Both the poles, you find, 

 attract both ends of the needle. Eeplace the needle by a 

 bit of annealed iron wire; the same effects ensue. Sus- 

 pend successively little rods of lead, copper, silver, brass, 

 wood, glass, ivory, or whalebone; the magnet produces no 

 sensible effect upon any of the substances. You thence 

 infer a special property in the case of steel and iron. 

 Multiply your experiments, however, and you will find 

 that some other substances, besides iron and steel, are 

 acted upon by your magnet. A rod of the metal nickel, 

 or of the metal cobalt, from which the blue color used 

 by painters is derived, exhibits powers similar to those 

 observed with the iron and steel. 



In studying the character of the force you may, how- 

 ever, confine yourself to iron and steel, which are always 

 at hand. Make your experiments with the darning-needle 

 over and over again; operate on both ends of the needle; 

 try both ends of the magnet. Do not think the work 

 dull; you are conversing with Nature, and must acquire 

 over her language a certain grace and mastery, which 

 practice can alone impart. Let every movement be made 

 with care, and avoid slovenliness from the outset. Ex- 

 periment, as I have said, is the language by which we 



