416 H. A. Rowland— Magnetic Permeability, and the 
civil engineer, and his training as such caused him to study 
closely every feature of the deposit, thus enabling him to 
furnish me with a mass of details which I could not otherwise 
have obtained. 
Morgantown, West Virginia, Oct. 14. 
Art. XLVI.—On the Magnetic Permeability* and the Maximum 
of Magnetism of Iron, Steel, and Nickel ; by Henry A. Row- 
LAND, C©.E., Instructor in Physics in the Rensselaer Poly- 
technic Institute, Troy, N. Y.+ 
In all mathematical theories of induced magnetization & 
quantity is introduced depending upon the magnetic properties 
of the substance, and without a knowledge of which the prob- 
lem is of little but theoretical interest; this quantity has always 
been treated as a constant, although the known existence of the 
maximum of magnetization showed it to be otherwise: the rea- 
son of this may perhaps be traced to a formula which Miiller 
has given to represent the magnetization of an electromagnet, 
and to the extreme difficulty of treating the subject in any other 
say These quantities as used by different persons are as 10 
ows: — ‘ 
k, Neumann’s coefficient, or magnetic susceptibility (Thomson). 
K, Poisson’s coefficient. : 
H, coefficient of magnetization (Maxwell), or magnetic permea 
bility (Thomson). : 
The relations of these quantities are given by the” following 
equations : — 
Se sas Hee 
4nK+3  u+2 
oa-l 8k 
"an ~ 4n(1—h) 
142k 
= is 
yh ck 4nK+ 
Very few determinations of oe of these quantiti 
been made in the case of iron and none in the case 0 
es have 
f steel, 
. re- 
* This word “ permeability ” has been proposed by Sir. William ye sen va 
place ‘conductivity ” as used by Faraday. (Thomson’s “ Papers on on 
and Magnetism” p. 484. Maxwell’s “Electricity and Magnetism, ae " 
+ Abstract of a paper in the Philosophical Magazine, August, | » Prep 
for this Journal by the Author. 
