More on Archimedes - NYTimes.com Re "Archimedes: Separating Myth From Science" (June 25): The story about Archimedes realizing in the bath that displacement of water could be used to test for the gold purity of a crown may or may not be true. However, the conclusion that it is not a practical test is based on a mistaken idea of how the test would be performed. It is not a matter of measuring "the tiny difference in volume between a crown made of pure gold and one made of a mixture of gold and silver." Archimedes knew that silver and gold had different weights per unit volume. His problem was how to measure the volume of a complicated object such as a crown. Volume displacement provided the answer. Then it would have been a simple matter of calculating the mass per unit volume. Richard W. Poeton Bennington, Vt.