40 PROFESSOR C. G. KNOTT ON MAGNETIZATION 
The nickel wires in these coils will be called L and M for ease of reference ; and the 
same letters may, if occasion arise, be used each to designate the corresponding 
anchor-ring coil as a whole. 
The wires L and M, with their stout nickel-bar terminals, formed two of the con- 
tiguous branches of the Wheatstone Bridge, the other branches and » being also 
made of nickel wire, so as to minimise the possibility of thermoelectric effects in the 
circuit. The resistances in B. A. ohms of the various branches at 13° C. were as 
follows, L) and M, being the resistances of the parts of L and M included in the 
magnetizing coils. 
| Wire. L | M r pB iby My 
| 
| 
| | 
| 
| Resistance . : 3°1237 | — 3-041 3°2413 3°1556 2957 2925 
The lengths and number of turns of the four magnetizing copper coils were as 
follows :— 
L-coils M-coils 
Inner. Outer. Inner. Outer. 
| Length of copper wire . |) -Cooremes elolbem as soo2 em. | 1297 em: 
| Number of turns : ? ih) 72 171 fal 
In the experiments to be described it was the nickel wire L which was studied ; 
hence, to reduce the magnetizing current in amperes in the coil L to fields in magnetic 
C.G.S. units we must multiply by 7°52. 
The magnetizing current was measured on a Kelvin graded galvanometer, which 
was calibrated 7m situ by comparison with a Kelvin ampere balance. 
The two anchor-ring coils L and M were enclosed in a porcelain vessel, through the 
side of which the various terminals were led. A quantity of asbestos wool was packed 
round the coils so as to reduce as far as possible the convection currents of hot air when 
the vessel was heated. The heating was effected by means of one, two, or more Bunsen 
burners, according to the temperature aimed at. After several hours’ heating the 
temperature of both coils became fairly steady ; and when the galvanometer indicated 
that a sufficiently steady temperature was reached, the necessary observations began 
to be made. The temperature of the wire L at any instant was indicated with great 
accuracy by the resistance of the wire, an independent experiment upon a wire cut 
