1. Published by permission of the Director, Bureau of Mines, U.S. Department of the Interior.
2. Physical chemist, Bureau of Mines, Central Experiment Station, Pittsburgh, Pennsylvania.
3. Collected Works of J. Willard Gibbs(Longmans, Green and Company, New York and London, 1928), Vol. 1, p. 63.
4. Reference 3, pp. 63–82.
5. See, for example, M. Bo^cher,Introduction to Higher Algebra(The Macmillan Company, New York, 1907), Chap. III.