46 On the Contraction and Expansion in Rods of Spring Steel. 

 from which is obtained for the steel rod No. 1, 



jl^ -0-293. 



Two other steel rods of almost the same dimensions as the rod 

 No. 1, were submitted to the same experiments. I content 

 myself with adducing the following results : — 



Steel rod No. 2. 

 B. T. 



35-83 34-77' 

 35-82 34- 



36-16 34-821 . ., ... lftOQ n 



36-14 34-84 f m anotner position; 16 *8 C. 



Mean.... B = 35-99, T=34*80, 



= 64-76 millims., =62-94 millims., 

 5=145-01 millims. 



^=0-295. 



'~£ > in one position; 12°'4 C. 



.-.q i- in one position; 22°'6 C. 

 L, > in another position; 22 0, 9 C, 



Steel rod No. 3. 

 3638 35- 

 36-33 35- 



36-40 35-1C 

 36-35 35- 



Mean.... B= 36-37, T = 35*10, 



= 65*43 millims., =63*48 millims., 



s= 145*16 millims. 



Hence in the mean for the three steel rods, the relation of the 

 lateral contraction to the longitudinal expansion is 



0-294. 

 It would be interesting to ascertain whether with rods of a 

 different section to that of those here investigated, the above rela- 

 tion would be as great. If that were the case, the assumption 

 here made would be thereby confirmed, that a hardened steel 

 rod may be considered homogeneous, and of the same elasticity 

 in different directions. Objections may be raised against this 

 assumption ; in fact it may be assumed that in the hardening, in 

 which heat flows from the axis towards the periphery, the elas- 

 ticity in the direction of the axis is different to what it is in direc- 

 tions rectangular thereto, and that the molecules in the external 



