st Office at Philadelphia in accordance with Section 199 of the Postal Laws and Regulations OF THE THE JOURNAL FRANKLIN INSTITUTE DEVOTED TO Science and the Mechanic Arts. ** EDITED BY PROF. EDWIN J. HOUSTON, A.M., PH.D., Chairman, PROF. ARTHUR DR. WM. H. WAHL, Secretary of the Institute. AUGUST, 1894. No. 2 MONTHLY, FIVE DOLLARS PER TEAR SINGLE NUMBERS, FIFTY CENTS, CONTÈNTS. The Graphics of the Efficiencies of the Steam Engine. By R. H. Thurston, Industrial Applications of Cellulose Thiocarbonates and Products Derived there- The Heating and Ventilation of Large Buildings. By Alfred R. Wolff, M.E., 81 100 III 116 . . 126 A Theory of the Actual Earth Pressure and its Application to four particular CHEMICAL SECTION: Investigation of a Bitumen from Park County, Montana. By Wm. C. Day and 139 149 Anthracite Coal near Perkiomen Creek. By Oscar C. S. Carter, Professor of State Weather SERVICE, Monthly Bulletin and Maps.-Supplement. PUBLISHED BY THE FRANKLIN INSTITUTE, PHILADELPHIA, (S) THE Franklin Institute is not responsible for the state. ments and opinions advanced by contributors to the Journal. THE GRAPHICS OF THE EFFICIENCIES OF THE BY R. H. THURSTON, Director of Sibley College, Cornell University. Among the many fragments of Rankine's work on the economics of the steam engine which have been left us as nuclei of later detailed and more complete studies, none, perhaps, better illustrates the remarkable perspicacity of the man than his statement of the principle properly governing the adjustment of the best ratio of expansion, and his exemplification of that principle by the application of the touchstone of financial result. James Watt, a century ago, and more (1782), patented his invention of the use of the expansive action of steam in the engine, with the purpose of effecting the most economical possible conversion of thermal into dynamic energy; but he was never able to secure those gains in the practical operation of the machine VOL. CXXXVIII. 6 which his mathematical computations had indicated as scientifically possible and as practically obtainable. A hundred inventors since the time of Watt have wrecked their fortunes, and thousands of engine builders and users have met with disaster, striking on the same rock. The vast discrepancy between the seemingly exact and positive predictions of the thermo-dynamic and mathematical theory of the engine and its practical results in everyday work have seemed to all the early engineers too great to be attributed to other than defects of construction and to errors in restricting the expansion of steam or in so constructing the machine as to make it impracticable to secure at once considerable expansion and steady motion. For a century it thus happened that efforts were constantly being made by inventors and builders to find some way of grasping that immense profit which was apparently just within reach by the simultaneous rise of steam pressures and the expansion ratio. It is only recently that we have learned precisely where the difficulties lie, and what must be the direction of improvement to insure the remedy of the still existing defects and further approximation to the thermo-dynamic conditions and to those results which are the ultimate object of every great invention relating to this wonderful machine. Watt discovered the facts which are now known to constitute the obstacle to success in the endeavor to carry out his principle and to gain full advantage in transformation of the heat-energy stored in steam; but he exhausted all his ingenuity in the endeavor to remove what he thought the main barrier to complete utilization of his idea-irregularity of action of a piston subjected to varying pressures— and probably never discovered that, with ever so smooth a motion, profitable expansion must be enormously restricted by that phenomenon, the investigation of which was the subject of his very first experiments with the old Newcomen model of the University of Glasgow. It was reserved for Daniel Kinnear Clark, in England (1852), for Hirn, in France (1855), and for Isherwood, in the United States (1860), to show that the primary source of this restriction of profit able expansion was to be found in the fact that the internal wastes by condensation of steam, consequent upon the heat-conducting character of the cylinder walls-to "cylinder condensation" as it is now generally, though, perhaps, inelegantly, termed-increase more rapidly than the gain by expansion, thus giving a low ratio of maximum economic value. Rankine and Clausius, and Thomson and Zeuner, built up the whole thermo-dynamic theory of the heat-engines; but it was only after a quarter of a century had passed that the differences between the ideal and the real heat-engines came to be fully understood, and that their effect upon the economical working of the machine was recognized. Rankine earned added fame by his declaration of the principles of finance bearing upon the case and by showing that here, as in every other task set the engineer, the results must be gauged by the final measure of all engineering—the work accomplished by the unit of coin paid out; but the effect of the Watt phenomenon did not enter into his computations, and its extraordinary effect upon the proportions of the steam engine remained to be revealed by the work of the last and the current decades. The essential principles affecting the proportions of the engine which will give the best results, all things considered, are probably all now familiar to every well-informed engineer and to many contemporary thermo-dynamists; and the exact methods of investigation of the subject will become equally familiar to all when the now numerous researches in the physics and the economics of the case, now in progress in the hands of numberless engineers and men of science, shall have fully revealed the data needed for their development. Graphical methods of representation are usually more intelligible to the engineer than are the algebraic processes; and this is especially true of the engineer whose genius lies in the direction of invention and of construction, rather than of theoretical investigation, and where the conditions to be studied and examined with reference to their relative interactions are numerous and where those mutual influences are obscure. An algebraic equation gives, in its solu |