Letters to the editor

To the Editor: The most interesting article by Professor Bennett on “Theory of Probability” published in the November 1933 issue of ELECTRICAL ENGINEERING, p. 752–7, called forth a “Letter to the Editor” by Mr. S. A. Smith, Jr., published in the January issue of ELECTRICAL ENGINEERING, p. 229–30. In this letter Mr. Smith raised a very important question about application of theory of probability to the problem of determining the proper number of spare units in the electric system.