BOOK I PART II
consists in the different numbers of the feet, of
which they are composed; and that of a foot
and a yard in the number of the inches. But
as that quantity we call an inch in the one is
supposed equal to what we call an inch in the
other, and as it is impossible for the mind to
find this equality by proceeding in infinitum
with these references to inferior quantities: it
is evident, that at last we must fix some stan-
dard of equality different from an enumeration
of the parts.
There are some (See Dr. Barrow’s mathe-
matical lectures.), who pretend, that equality
is best defined by congruity, and that any two
figures are equal, when upon the placing of
one upon the other, all their parts correspond
to and touch each other. In order to judge of
this definition let us consider, that since equal-