316 
1400 
1200 
1000 
800 
600- 
400 
200 
On Random Occurrences hi Space and Time 
Fig. I. Lengths of intervals in an iiidetinitely long time. 
I 
OBSERVED 
CALCULATED 
/ff = *363 
m = 2-496 
10 
Seconds 
15 
20 
III. Frequency of Occurrences in limited Periods of Time. 
The second question to be considered is that of the frequency of occurrences of 
the event in a limited period T. From a practical point of view this is, perhaps, a 
more important one than the preceding. 
{a) It will be shown that the hypothesis has to be made that there was no 
occurrence within the " closed-time " 13 before the beginning of the period T, so that 
the material used is only a portion of that which can be used when considering 
events occurring in an indefinitely long time. Now, in the mathematical theory 
