APPENDIX TO CHAPTER XIII 373 
By limits we may pass from income which flows at a uniform 
rate to any income stream. Evidently, therefore, any con- 
tinuous income-stream may be represented by a curve (Fig. 37) 
of which the ordinate represents the per annum rate of flow at any 
  
C 
B 
A 
E F ? 
Fic. 37. 
point of time, and the area EC between any two ordinates BE 
and CF represents the total income which flows within the time 
intercepted between those ordinates. 
For the case of uniform flow, the continuous income stream 
is represented in Figure 38 by the area OB. OA represents the 
C D> 
  
  
  
0 
Fic. 38. 
rate of income, and OC represents the capital-value of this in- 
come. This capital-value remains constant, as shown by the 
PERS EE