EXPERIMENTAL RESEARCHES ON DRAWN STEEL. 
13 
than the mean of the cold values, a result which corresponds to a negative coefficient; 
later on, after the reversal, the hot is larger than the mean of the adjacent cold 
values, a result which corresponds to a positive coefficient, and this positive coefficient 
will, no doubt, continue uj) to maximum induction. 
Both before and after reversal heating appears to produce much larger effects than- 
cooling. 
Under alternate applications of heat and cold, the coercive force is greatly lessened, 
and now lies at less than 11-2, instead of its former value 13-5 hot and U’O cold. 
12. In the next place the effects of alternate changes of temperature on residual 
magnetism were studied. 
The same wire was again employed, and, starting from the demagnetised state, a 
small force was applied, and the residual magnetism subjected to heating and cooling. 
Then stronger forces were successively applied and, in the same way, at each step 
the coefficient was determined; after the maximum had been reached, part of the 
magnetism was removed, a step at a time, and again the temperature coefficient 
was examined at each stage. Table IV. is an abstract of the results so obtained. 
Table IV.—Effects of Heating and Cooling on Residual Magnetism for Progressive 
Magnetisation, 
H 30 Piano Wire. 
MaErnetisinp’ force, 
" H." 
Residual 
intensity. 
Temperature 
coefficient, 
a. 
Permanent 
chansie, 
/3. 
Initially, 
Finally, 
b- 
X 10-^ 
X 10-3 
10-32 
107 
91 
+ 3-10 
- 15-0 
19-52 
GIG 
572 
+ 4-53 
- 7-0 
23 - 33 
838 
794 
+ 3-59 
- 5-0 
(About 100) 
1022 
9G7 
+ 2-82 
- 5-0 
(Small negative force) 
837 
840 
+ 4-34 
+ 0-4 1 
- 10-54 
7G2 
775 
+ 4-42 
+ 2-0 
- 15-03 
270 
312 
+ 3-GG 
+ lG-0 
-15-93 
114 
157 
+ 1-88 
+ 38-0 
— 
21 
G4 
- 2-90 
+ 204-0 
- 12 
+ 30 
- 4-70 
— 
-G2 
-20 
+ 25-00 
-224-0 
From this table the influence of the intensity on the magnitude and sign of the 
coefficients a and can be traced. 
In the first place, the coefficient rises to an early maximum and then falls to a 
minimum at the highest intensity; on the return path the coefficient again attains a 
niaximum, which occurs at a liigher intensity than before, and after this it continually 
