570 
Transactions of the Boyal Society of South Africa. 
weight for a range of weights from 50 to 400 grammes. The period of 
oscillation of the spring with various weights attached was determined, 
and the equivalent mass of spring and added weight calculated from the 
formula 
Subtraction of the added weight from M' now gives the equivalent mass of 
the spring alone. 
The last column gives the equivalent mass of the spring as derived from 
the above theory. 
Table of Eesults. 
= 164 grammes. Iv— 16-96 X 979*7 dynes. 
M. 
T. 
M'. 
m' (obs.). 
m' (theor.). 
0 
•3991 
67-1 
67-1 
65-5 
10 
•4223 
75-1 
65-1 
64-8 
20 
•4469 
84-1 
64-1 
63-5 
50 
-5139 
111-2 
612 
61-0 
100 
-6138 
158-6 
58-6 
58-8 
2001 
•7817 
257-3 
57-3 
571 
250-3 
•8537 
306-8 
56^5 
56^7 
400-1 
1^0390 
454-2 
541 
55^7 
What difference there is between the observed and the theoretical value 
may be put down to the change in the value of K for different loads ; the 
value increases with the load, but more elaborate experiments will be neces- 
sary in order to assign definite values of K for different loads. 
The experiments show that (1) the assumption of uniformity of the 
spring introduces no error, (2) the rough approximation usually given for 
the equivalent mass is inadequate, (3) no difference aj^pears between the 
static and the dynamic value of K. 
