Shooter's Hill, August 3.
_Achilles and the Tortoise._--Your correspondent will find references
in the article "Zeno (of Elea)" in the _Penny Cyclopædia_. For Gregory
St. Vincent's treatment of the problem, see his _Quadratara Circuli_,
Antwerp, 1647, folio, p. 101., or let it alone. I suspect that the
second is the better reference. Zeno's paradox is best stated, without
either Achilles or tortoise, as follows:--No one can go a mile; for he
must go over the first half, then over half the remaining half, then
over half the remaining quarter; and so on _for ever_. Many books of
logic, and many of algebra, give the answer to those who cannot find it.