146 Transactions of the American Institute. 



— see ! as it progresses, how the tacks rush toward it, and observe 

 also how they cling to one another until now they 'form a train and 

 follow the stone, as it disappears from view. Surely it is " the affec- 

 tionate." 



The lodestone, however, attracts steel as well as iron, as you see, 

 now that I have substituted these steel needles for the iron tacks. 

 Apparently the lodestone acts alike on both, but let us examine into 

 this. I have here a piece of copper wire, which I am wrapping 

 around one end of this short piece of soft iron. I now have made a 

 handle of wire, by which I can draw the other end of the iron through 

 these iron-filings, which you observe as huge grains on the screen. 

 The iron has ploughed a clear track through them. I again draw it 

 through the same line, but you see that I have placed against its 

 other end the lodestone, and you see the filings crowding in toward 

 the iron from outside the bright track, and now the iron has actually 

 taken off the plate a considerable breadth of them. I have placed 

 aside the lodestone and again I draw the end of the iron across this 

 plate in another direction. See, again it leaves behind it the bright, 

 clean line, and not a particle of iron adheres to it in its progress. I 

 now substitute for the soft iron a piece of stout darning needle. It 

 also leaves behind it a clear line, and not a grain of iron attaches 

 itself to it; and drawing it again through this line with the stone at 

 the other end, you see that it, like the soft iron, draws to itself the 

 filings. But now observe the difference when I lay aside the lode- 

 stone and draw alone the steel needle through the filings. See the 

 iron brush which has formed on its end. I pull off the iron filaments. 

 Again they form as I draw it across another diameter of the circle. 

 Thus we find that iron is only temporarily, but steel is permanently 

 magnetized by contact with the lodestone. Indeed, we find, on fur- 

 ther examination, that the lodestone has endowed the steel with all 

 -of its magnetic properties, and therefore we can now set aside the 

 stone and use in its stead these various steel bars and suspended 

 needles, of more convenient forms, which we will suppose have 

 derived their magnetism from contact with the lodestone. 



Thus from the magnetism furnished us by nature in this stone I 

 have permanently affected this piece of steel with extraordinary pro- 

 perties,, but there are other means of obtaining them in a far more 

 exalted degree. The most powerful yet reached has been accom- 

 plished 'by means of this instrument — the great electro-magnet of the 

 ..Stevens -Institute of Technology. 



Jlere <yn each of these two strong tables rests four large brass 



