American Scientist

To the Editors:

In discussion of the Lambert W function (Computing Science, March–April), Brian Hayes offers as description of the Euler number e, the limiting value of a compound interest expression.

As a physical chemist, I would observe that there are a number of natural decay processes that e well describes, including first order chemical rate processes, radioactive decay, and electrical RC circuit behavior.

All of these result from integration over time of the differential equation, –dX/dt = kX, where X is some physical quantity (concentration, charge) and k is a rate constant. The result is X = e^(–kt), leaving out the constant of integration.

Thus, I suggest that e is not merely some useful mathematical construct, but a description of some widespread natural phenomena.

David M. Wetstone
Hartford, Connecticut