[20] The literature is considerable; in the form of special economic studies as well, of course, as in the standard histories and documents already named at the head of this chapter. The bibliography in Cleveland and Powell is to be commended. The long-promised Economic History of the United States in preparation by the Carnegie Institution will doubtless add much. Among special references, the following authors are typical; titles of others being given in the Catalogue of the Bureau of Railway Economics, 1912, under the names of states. Wisconsin. B. H. Meyer, _Bull Univ. Wis._, XII, 1892. Texas. C. S. Potts, _Bull. Univ. Texas_, No. 119, 1909. Missouri. J. W. Million, University of Chicago, 1896. Michigan. H. E. Keith, University of Michigan, 1900. Southern states. U. B. Phillips, History of Transportation, etc., 1908. Pennsylvania. A. L. Bishop, The State Works of Penn., 1907. Illinois. Davidson and Stuvé, History, etc. Nebraska. _Quarterly Journal of Economics_, VI, p. 337 _et seq._ On typical city participations; J. H. Hollander on the Cincinnati Southern, _Johns Hopkins University Studies_, 1894: U. B. Phillips, _op. cit._, on the Western and Atlantic; on Philadelphia, Ringwalt, _op. cit._: on municipal aid in Massachusetts, 2nd Ann. Rep. Mass. R.R. Com., etc. [21] Potts, _op. cit._, p. 85. [22] Thesis of Miss Ethel Jenney at Radcliffe College, under direction of Professor A. B. Hart. [23] B. H. Meyer, _op. cit._, p. 362. [24] Miss Jenney, _op. cit._ [25] Bogart, p. 219; Coman, p. 239. [26] For the Federal land grants, the standard works of Donaldson and Sanborn are best. Also, H. K. White, History of the Union Pacific Railroad, 1895: (The chapter on construction is reprinted in Ripley, Railway Problems, Chap. III.) E. V. Smalley, History of the Northern Pacific Railroad, 1883: etc. [27] Details are in the Pacific Railroad Commission Report; 50th Cong., 1st sess., Exec. Doc. 51, 9 vols. The final settlement is described in _Quarterly Journal of Economics_, XIII, 1899, pp. 427-444. [28] A more detailed account of the rise of the Harriman system is in vol. II. CHAPTER II THE THEORY OF RAILROAD RATES Analysis of railroad expenditures, 44.--Constant v. variable outlays, 45.--Fixed charges, 46.--Official grouping of expenses, 46.--Variable expenses in each group, 51.--Peculiarities of different roads and circumstances, 56.--Periodicity of expenditures, 61.--Joint cost, 67.-- Separation of passenger and freight business, 68.