H. A. Rowland—Studies on Magnetic Distribution. 455 
taken at one point and Q and Q at another point whose dis- 
tance from the first is /, we shall have the four equations 
Q=C, Q=—© (Actes, 
A+1 
A~1l1 C 
Q- = Aa 0% Ges mA (Aet+e), 
Calling i oe H and “ = G, we shall find, on eliminating 
Cand A and developing «” and €~, 
2/GH+1 
dome a GO 
or to a greater degree of approximation, 
1 GH+1 
re = HW 10(oS 41) 6), wee > « Wa) 
Before applying these formule to any series of observations, 
the latter should be freed from most of the irregularities due to 
accidental causes. For this purpose the following Tables have 
been plotted and a regular curve drawn to represent as nearly 
as possible the observations; in other cases a column of differ- 
ences was formed and plotted. In either case the ordinates of 
the curves were accepted as the true quantities. But for fear 
that some may accuse me of tampering with my observations, [ 
have in all cases added these as they were obtaine 
The correction is necessary, because small irregularities in 
the observations will produce immense charges in r?. 
Table IV. contains some of the best observations I have 
obtained. It is from a bar 57 inches long with a helix 13 
inch long in the center to magnetize it. Hach quantity is 
the mean of six observations, these being made on both ends 
of the bar and with the current in opposite directions. : 
In this table a source of error was guarded against which 
ave not seen mentioned elsewhere. When a bar of iron 
to reach its permanent state. : : 
On looking over column 6, which contains the values of 
if : 
7 Eo R’ay (equation 7), we observe that as Q’ increases, 
the value of R’aw first increases and then decreases. Now itis 
hot probable that R’ undergoes any sudden change of this sort, 
