222 Methods of making Magnets independent of lemperature^ 



irons and steels, and is particularly small in hardened cast irom- 

 Certain hardened nickel steels have very small negative coefficients. 



2. The discovery of negative coefficients in mnsic wires. 



3. Change of the sign of the coefficient by alteration of (a) temper 

 and (b) dimension ratio, and hence methods of obtaining zero co- 

 efficients. 



4. Some relations between the dimension ratio and self-demagnetis- 

 ing factor, temperature coefficient, and permanent loss of magnetism 

 after alternate heatings and coolings. 



An important consideration in any practical application to mag- 

 netic instruments of magnets with zero coefficients is the constancy 

 of the zero state. 



It is not yet possible to speak precisely on this point, but two 

 wires which had been prepared by adjustment of temper to have 

 zero coefficients in June, 1896, and since then had been lying on a 

 shelf, and in the vicinity of other magnets, when tested nine months 

 later, had not altered so much as to have a coefficient of practical 



