414 Correspondence of J. Nickles. 
These classes are subdivided into families which rank according to the 
number of branches or disks of which they are composed; thus the rec- 
tilinear electro-magnet having only one branch will form the first family. 
The electro-magnet with two branches will serve as a type of the second 
family which will be that of bifurcated magnets, and the trifurcated 
electro-magnets or those with three branches form the third family ; and 
finally the fourth family is composed of multifurcated electro-magnets, 
i.e., those with more than three branches. The families of electro-mag- 
nets stop here; there are consequently no quinto, sexto ... n fureated 
electro-magnets, experience having shown that the properties of electro- 
magnets with more than three branches are very much the same, one 
new branch adding no new property. 
The same method is followed with disk-shaped electro-magnets whose 
name is derived from dromos, course, in order to distinguish their most 
characteristic property, that of turning or revolving. These electro- 
magnets are divided into two groups, viz: 
Ist. Para-cireular, 2d. Circular. 
The first group is subdivided into para-circular uni-dromes, bi-dromes, 
tri-dromes, or multi-dromes, according as they are composed of one, two, 
three or more disks, in the same manner as for the branched electro- 
nomenclature we shall have a bifurcate monokneme electro-magnet, with 
antinome and heterodynamic poles which consequently teaches us the 
properties of this apparatus just as the expression “sulphate of potash 
us much more of the composition of that ternary than did the Sal 
polychrestum Glaseri of the alchemists. f 
If the question is in regard to the common horse-shoe magnet we 
shall say Bifurcated dikneme, for the circular magnets with three disks 
before described ;+ then we shall call them tridome dikneme; that of the two 
disks} we shall call bidome dikneme with isodynamic poles or with hetero- 
dynamic poles according as the helix is placed symmetrically or otherwise. 
” * This Journal [2], xv, 107 and 883, + Vol. xvi, p.110. — ¢ Vol. xx, p. 101. 
