of the Magnetical Principle in Ferruginous Bodies. 359 
developing the magnetic properties of any ferruginous body, 
simply consists in giving arrangement to the magnetic particles. 
And the manner in which this is accomplished, is, I conceive, 
very Well illustrated, by the experiment I shall next describe. 
Let there be several small magnetic needles (those I used 
were an inch in length), with a small stand of brass for each, 
holding a fine point, on which the needle may traverse. Ar- 
range them in a row on an east and west line, and at such a dis- 
tance from each other, that when the needles are in order, and 
forming a continuous line, their extremities may be about the 
fiftieth of an inch asunder. In this condition they will be easily 
arranged (if they do it not spontaneously) in a regular series, 
with all their north poles one way, when they may be considered 
as representing the particles of a small magnet, and in a state to 
afford a striking illustration of the probable manner of action of 
a strong magnet on a small magnetizable body. For, on pas- 
sing the north pole of a bar-magnet over the series, beginning 
at the south end of the row, and carrying the magnet at an inch 
or two elevation above the needles, according to its strength, in 
a gradual manner, to a little beyond the other end of the series, 
all the needles will, in succession, turn round, and finally ar- 
range themselves with their poles in the opposite direction to 
that they had at the commencement. Now, this effect resembles 
the change of poles produced in a weak magnet, by passing 
along it the pole of a strong magnet,— for in both cases the or- 
der of the poles is analogous, the pole where the operation ter- 
minates being the reverse of the denomination of the pole passed 
over. And, in like manner, commencing with the needles in 
disorder, which resembles the condition of an unmagnetized 
piece of iron, the mere juxta-position of one pole of a magnet, 
or the passing across it of a single pole, arranges the series in a 
magnetical order, illustrating the developement of the previous- 
ly neutralised magnetic principle. But, besides these resem- 
blances, the principles exhibited by these experiments, may be 
applied to the explanation of the various processes for magne- 
tizing iron, and of several phenomena connected with the mys- 
terious agent in question, which have been generally considered 
as difficult and obscure. 
