Sxc. 8] CONCEPT OF RATE OF INTEREST 201

constancy enters, the two senses will involve two unequal
magnitudes, we have here represented or implied thirtytwo
 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 followmg.