EXPERIMENTS upon MAGNETISM, 



No. XXXIX. 



Experiments upon Magnet ifm. Communicated in a Letter 

 /(? Thomas Jefferson, Prcfuient of the Philof optical 

 Society, by the Rev. James Madison, Prejident of 

 William and Mary College. 



April, 1798- 

 Dear Sir, 

 Read May XN the revicw of my philofophical courfe for 

 4, 1798. J|_ this year, I have been led to make fome expe- 

 riments upon magnetifm, which appeared to fall within 

 the views of the American Philofophical Society. It is 

 for this reafon that 1 have taken the liberty of communi- 

 cating them to you. 



Few fubje6ls in natural philofophy are, in reality, more 

 interefting to mankind than magnetifm ; and yet, the in- 

 vifibility of the agent, and the confequent difficulty of 

 purfuing a caufe, which feems to be fubje^ted to none of 

 our fenfes, has greatly reftridled the progrefs of know- 

 ledge in this branch of phyfics. Some phenomena, 

 which have long attracted the attention of the philofopher, 

 and excited the admiration of the vulgar, have received 

 different folutions, grounded upon as many different hy- 

 pothefes. No method appears to have been adopted to 

 fhew the fallacy of the one, or the verity of the other. 

 They flill remained as hypothefes. The following expe- 

 riments, fimple as they are, give a folution, which car- 

 ries with it occular demonftration ; and, as the jufl expli- 

 cation of every fa6l is a real advance in philofophy, I trufl 

 they will not be thought unworthy of attention. 



The phenomena to which I allude are thofe, which 



magnets, placed upon paper, exhibit with filings of iron, 



when they are fprinkled about them. Many ingenious 



U u 2 men 



