Between two Similar Solid Numbers exist two Mean Proportionals/Mistake

Source Work

 * Book $\text{VIII}$
 * Commentary on Proposition $19$

This mistake can be seen in the edition as published by Dover: ISBN 0-486-60089-0.

Mistake

 * [Euclid] next forms the products of $c, f$ respectively into the mean $b d$.
 * Then $abc, cbd, fbd, def$ are in the ratio of $a$ to $d$ etc.
 * For

The middle line of the above is incorrect -- it ought to read:
 * $c b d : f b d = c : f$