267 
of Metal Rods with rounded ends. 
Using these figures, the ratio — has the following values : — 
V 6 
Steel 1-001 
Copper ... ... ... ... ... 1-0015 
Aluminium ... ... ... ... 10026 
so that we get the following table of velocities : — 
Observed 
Calculated 
Isothermal 
Adiabatic 
Steel 
16,820 
16,750 
16,770 
Copper 
12,060 
12,010 
12,030 
Aluminium 
16,620 
16,580 
16,620 
The agreement between the first and last columns is very close 
indeed, the difference in the worst case, that of steel, being only 
1%. This is well within the limits of experimental error, and we 
may therefore assume that Young’s Modulus has the same value 
whether the loading is slow or sudden. 
We now turn to a more detailed consideration of the experi- 
mental work. The rods were adjusted by means of the brass 
regulators (A, Fig. 2 A). The upper ends of the suspending cords 
passed through small holes in the faces of these regulators, and 
then through similar holes in the blocks ( B , Fig. 3) to the pegs, A, 
18—2 
