Lecture on a new property of Magnetism. 527 



further advances. I give you that kind of action which Volta used 

 when he first discovered the battery. I may not bring my tests 

 [large bars of steel weighing many pounds] in close contact with 

 these poles ; if I do, perhaps I shall never get them off again, or 

 at least during the lecture. I must put something between them — 

 a piece of board, for example — which I can easily lift off again. 

 Contact is made, and we have now the magnet in full power; you 

 may see the difficulty of moving the heavy mass of iron away from 

 the poles. I might almost pull the whole table down by the attrac- 

 tive force of the iron beneath influencing the magnet through the 

 thickness of this board. You have seen nothing like this power 

 before. It would suspend many tons weight of iron. It is only by 

 seeing facts of this kind that you become aware of the enormous 

 power I am about to use in the applications I shall make to show this 

 particular kind of phenomenon. I take two bars of iron ; on making 

 contact they become one bar. The moment contact is broken it is 

 unmade ; and the beautiful condition which we have of making and 

 unmaking, of giving or destroying an extraordinary force, is one 

 essential point in the manifestation of this phenomenon. I should 

 like you to see the condition of the magnetic curves as shewn by 

 means of this arrangement, and which we can soon exhibit by sprink- 

 ling a few of these nails on the mill-board. You saw where the 

 two poles were placed; you see how inert the nails are at present. 

 We will make them magnets, and then see how the curves run to- 

 gether. It is almost unmanageable, for as soon as a plate covered 

 with nails approaches the magnet, it attracts them so powerfully as 

 to strip it entirely of its contents. You see here an illustration 

 of the tales in the Arabian Nights' Entertainments. Mark the way 

 in which new powers are given, and bodies of enormous weight are 

 held firmly together. Observe this line of nails actually rising into 

 the air, and tending to make curves such as I shewed you on a 

 former occasion. It is a curious and beautiful thing quietly to look 

 at this action. This is merely incidental ; I only shew the point to 

 illustrate the power of the magnet. When contact is made, if I lay 

 a few nails quite at the extremity of the mill-board, they fly instantly 

 to the others in the centre. You see how strong the curves are 

 here, compared with the line of force, by the manner in which they 



