370 Dr. Lamont on the most advantageous Form of Magnets. 



the magnets, would consist in procuring hardened steel bars of 

 different forms, magnetizing them to saturation, and investiga- 

 ting by measurement for every form the above-mentioned deter- 

 minations. By this method I have instituted different experi- 

 ments, but have given to them no great extension, because I 

 have found another way which attains the desired end more 

 simply and more surely. 



A magnet is composed of magnetic molecules. If the mole- 

 cules were separated, it would appear that every molecule forms 

 a small magnet with a determinate quantity of positive and ne- 

 gative magnetism ; and this is what I denote by independent mag- 

 netism. As soon as the molecules are put together, each induces 

 in the rest new magnetism, and to the independent magnetism 

 of each molecule there is added a more or less considerable 

 quantity of induced magnetism, according to the situation which 

 the molecule occupies in the magnet. 



The whole effect of a magnet is regulated by the independent 

 and induced magnetism of the molecules. 



A magnet is then magnetized to saturation when every mole- 

 cule possesses the greatest possible independent magnetism ; from 

 which of course it follows that in a bar magnetized to saturation 

 all the molecules have equal independent magnetism. 



Now if we introduce a soft iron core of tolerable length into 

 a very long spiral, through which a galvanic current passes, 

 it is known that the same magnetizing force is exerted upon 

 every molecule of the iron core ; that is to say, equal independent 

 magnetism is imparted to each molecule, and the mutual induc- 

 tion of the molecules comes then into operation as in the mole- 

 cules of a magnet. From this it results that the distribution of 

 the magnetism in an iron core placed within a long spiral, and 

 that in a magnet which is magnetized to saturation, will be the 

 same ; and the laws under the limitations above-mentioned can be 

 determined quite as well by iron cores as by magnets. But by 

 substitution of iron cores, the great advantage is obtained, that the 

 investigation is not only more easily executed, but also the dis- 

 turbing influences which arise from the unequal or dispropor- 

 tionate hardness of different bars, and the consequent uncer- 

 tainty whether, in the magnetizing, the point of saturation* is 

 really reached, totally disappear. 



* If a needle is rubbed with a pair of magnetic bars which are somewhat 

 larger than the needle itself, and this rubbing is continued till the needle 

 no longer receives additional magnetism, it is said to be " magnetized to 

 saturation," although it is not proved whether a far greater magnetism 

 might not be imparted by more powerful instrumental means. On the 

 magnitude of the means which is required to communicate the maximum 

 of force, no satisfactory investigations have hitherto been instituted; and 



