Hl. A. Rowland—Studies on Magnetic Distribution. 388 
necessary at present to consider the cause of this apparent dis- 
crepancy between theory and experiment; suffice it to say that 
the explanation of the phenomenon is without doubt to be 
sought for in the variable character of the magnetizing function 
of iron. All I wish to show is that the attraction of iron to a 
magnet, especially when the two are in contact, is a very com- 
plicated phenomenon, whose laws in general are unknown, 
and hence is entirely unsuitable for experiments on magnetic 
distribution. 
found = for short magnets, where the method suggested is 
very good. 
The similarity of this method to that used by Gauss in deter- 
mining the distribution on the earth is apparent. 
_A fourth method is similar to the above, except that the 
direction of the lines of force around the magnet are meas 
and calculated instead of the force. 
_ the last two methods are very exact, but are also very labo- 
ous, and therefore only adapted to special investigations. 
us, by the change in direction of the lines of foree around 
the magnet, we have a delicate means of showing the change 
In distribution, as, for instance, when the current around an 
tro-magnet varies, 
The fifth method is that used lately in some experiments of 
Mr. Sears (this Journal, July, 1874), but only adapted to tem- 
porary’ magnetization. At a given point on the bar a small 
coil of wire is placed, and the current induced in it measured 
by the swing of the galvanometer-needle when the bar is 
