Expansion Curves

Abstract

IN your issue of October 8 Prof. John Perry describes in a letter “an exceedingly simple, ingenious method” of plotting the so-called polytropic curve representing the law pvⁿ = constant, which method he found in a pamphlet by Mr. E. J. Stoddard, of Detroit. I may be permitted to state that this method was published for the first time eighteen years ago by Prof. E. Brauer in the Transactions of the Society of German Engineers, 1885, p. 433, and since Prof. Brauer's publication this method has been used in a number of treatises on thermodynamics published in Germany and France. It has been given for years in the very valuable handbook “Huette,” which is undoubtedly known to Prof. Perry. Is it not surprising that a method which Prof. Perry himself considers very important should have to reach England from Germany by the circuitous path of the United States?