230 GREAT MEN OF SCIENCE 



Steel molecule of the magnet contains in itself a small per- 

 manent circular current; magnetisation would then only 

 consist in directing all these circular currents of the in- 

 numerable iron or steel molecules in the same sense. As 

 against this idea, and in the immediately subsequent time in 

 an increasing degree, the objection existed, that the con- 

 tinued maintenance of such currents without a source of 

 power would not be possible. This objection has only quite 

 recently fallen to the ground, when a continued circulation 

 of electricities in the atoms and molecules was proved to 

 exist in quite another manner, by special facts (at first by 

 means of Hittorf's cathode rays). 



But even without these recent discoveries, Ampere's 

 ideas bore immediate fruit. Arago had noticed that the 

 connecting wire of Volta's pile coats itself with iron filings, 

 which were previously entirely non-magnetic, but afterwards 

 show permanent magnetism. He showed this to Ampere, 

 who immediately said that a current carrying coil would turn 

 steel needles placed in its axis into magnets, having north 

 and south poles arranged in a manner which could be pre- 

 dicted. This gave the means of making much stronger 

 magnets than had ever been possible before by the use of the 

 lodestone. Furthermore, the way to the electromagnet was 

 open, which retained or lost its power at will by closing and 

 opening the current; it was only necessary to use soft iron 

 instead of steel in the core. We know what an enormous 

 number of applications have been found for this; the electro- 

 magnet is the main constructional element of a large range of 

 electrotechnics, from the electric bell to the electric loco- 

 motive. 



