Additional Notes. 397 



very small portion of the horizontal bars intcndi-d to be made nuig- 

 netical, between the joint forces of two or more bars already 

 raagnetical, and, by sliding tliem from end to end, every part ot 

 the line of bars became successively included ; and tlius bar>, 

 possessed of a very small degree of magnetism to begin \\ith, 

 would, in a very few times sliding backwards and forwards, make 

 the other ones much more magnetical than themselves, which 

 are then to be taken up and used to touch the former, which are 

 in succession to be laid down horizontally in a \mcr— Botanic 

 Garden, Tart I, Canto ii, 1. IQS, note. 



Dr. Knight's method of making artificial magnets, referred to 

 by Dr. Darwin in the abvove-mentioned note, was as follows: 

 He reduced iron to a very subtle powder, made it into a paste with 

 oil, moulded the composition into pieces of a convenient form, 

 dried them before a moderate lire, and then imparted to them the 

 magnetic virtue, by placing them between the extreme ends of his 

 large magazine of artificial magnets, for a few seconds or more, as 

 he thought requisite. 



After Michel, the manufactory of artificial magnets received 

 further improvements by JNlr. Canton, in I75(i, and by M. An- 

 theaume, in 1 7QO. 



Note (L), p. 40.— Among other attempts to extend the bounds 

 of chemistry, it has been lately proposed to place the magnetic 

 fluid in the list of its subjects. Accordingly, several writers have 

 considered this fluid as a chemical agent, and explained its pheno- 

 mena on corresponding principles. Among these, ])r. Darwin, in 

 the Additional Notes to his Temple of Nature, proposes tlic follow- 

 ing hypothesis. 



I. Magnetism coincides with electricity in so many important 

 points, that ihe existence of tico ma<^netic ethers, as well as of two 

 electric ones, becomes highly probable. 



3. In a common bar of iron or steel, the two magnetic ethers 

 (which, for the greater ease of speaking, may be called arctic ether 

 and antarctic ether), exist intermixed, or in their mutral .tale : in 

 tliis state, like the two electric fluids, tliey are not cognizable by 



the senses. 



3 When these two magnetic ethers are separated from each 

 other, and the arctic ether is accumulated in one end of an iron 

 or steel bar, which is then called the north pole oi the magnei; 

 and the antarctic ether is accumulated in the other end of die bar, 

 which h then termed the south pole of tbo magnet, they becou^e 



