Sxc. 8] CONCEPT OF RATE OF INTEREST 201 
constancy enters, the two senses will involve two unequal 
magnitudes, we have here represented or implied thirty- 
two possible magnitudes. The means for expressing time 
exchanges between goods of the same kind thus present 
an embarrassing variety. But since it is easy to proceed 
from any one of them to all the others, it is evident that we 
need not, in general, employ more than one. The one 
which is practically the simplest, and which, therefore, we 
shall hereafter employ in this book is: the rate of interest 
per annum reckoned annually and considered as a premium 
on the goods of one year compared with those of the year follow- 
mg.