for June this year £1,772. The time from Arlington to Harvard Square, 4 miles, is twenty minutes, equal to 12 miles per hour, while the average speed on the elevated roads, in New York, is only 10.89 miles per hour. The company expected to run 15 miles per hour, and had seven hundred and seventy-six cars, at a cost of £200 each, and it would cost £20 each to turn them into electric cars. The average cost of motive power by horse for the past six months is 5d. a mile, which does not include drivers, starters, conductors, and repairers of track. From experience on the Allston road, with the disadvantages of a faulty conductor and the power station being too distant, the cost for fuel to supply current is only d. per car-mile; while the cost of power, engineering, engineers, and all other expenses amounts to rather over 1d. per car-mile. The estimated cost of taking care of the motors and overhead line is 1d. per car-mile, so that working by electricity would lead to a saving of 2d. per car-mile. E. R. D. The Magnetic Permeability of Soft Steels. By GEORGES HENRARD. (La Lumière Électrique, 1889, vol. xxxiii., p. 593.) Some dynamo builders having decided to use cast steel for the field-magnet cores and frames of their machines, the Author made experiments at the Montefiore Institute, Liége, in order to find steels sufficiently permeable to be employed for the purpose. The apparatus used was one described lately in 'La Lumière Électrique by himself and Mr. Melotte. The tests were made on specimens of steel made at Angleur, obtainable of all degrees of hardness. The most permeable are very cheap; all could be cast, and welded; and No. 6, which costs 78. 6d. per cwt., is softer than ordinary commercial wrought-iron, the carbon contained being only 0.1 to 0.3 per cent. A specimen of wrought-iron No. 4, of very good quality, and a specimen of malleable cast-iron from the Herstal foundry, were tested for comparison; the cast-iron was a mixture of grey and white pig, and had been decarbonized by heating along with sesquioxide of iron Fe, O. The Author states that, with a magnetic field of a strength equal to 240 C.G.S. units, the bar of malleable iron gave a specific induction of more than 15,000 C.G.S.; whereas Dr. Hopkinson, in a work published in 1885, gives 12,408 C.G.S. as the maximum for the metal, with the same field. Three Tables are given; the first for permeability, in which H is the strength of the field in C.G.S. units, and the permeability; the specific induction being therefore B H; the second gives the mechanical properties, and the third the chemical analysis. The permeability of a steel cannot be judged of by its percentage of carbon merely, as small percentages of other elements alter the results greatly. For instance, steel No. 5.5, which should be softer and more per[THE INST. C.E. VOL. XCIX.] = 2 L meable than No. 5, gave a poorer result owing to having a greater percentage of manganese. All these steels have a high permeability, and another advantage is that it is not necessary to use ferroaluminium in pouring them. From Table 1 the following numbers are extracted for a field of 250 C.G.S. units the permeability was, for steel No. 6, 100; No. 5.5, 80; No. 5, 80; No. 4.5, 86; No. 4, 76; No. 3.5, 80; No. 3, 74. Wrought-iron, No. 4, 80; malleable cast, 60. The Author draws special attention to steel No. 6; and then gives the following tests for specific resistance at 68° Fahrenheit:: The Influence of the Rotation of the Earth on Moving Bodies. By T. VON BAVIER. (Zeitschrift des Vereines deutscher Ingenieure, 1889, p. 862.) It has often been observed that in railway lines running north and south there occurs, in course of time, an appreciable displacement of the rails, always more noticeable on the right-hand side. This is, as the Author remarks, chiefly due to the effect of the rotation of the earth on its axis, the normal condition being that with a train travelling in such a direction and equally loaded there is a greater pressure on the right-hand side than on the left. In N. latitude 51° a man weighing 165 lbs., running at the rate of 13 feet per second from north to south, sustains a horizontal pressure towards the east equal to 54 grains, which, acting at the centre of gravity of the body at say 3 feet 3 inches above the ground, necessitates an extra pressure on the right foot of 0.63 oz., in order to maintain the vertical position of the body. In going from south to north the proportion is the same; in the southern hemisphere the extra pressure would come on the left side. With varying directions the force is, of course, proportionately varied. In the case of an express train, weighing say 400 tons, travelling northwards at the rate of 50 miles an hour, the extra pressure on the right-hand or eastern rail amounts to 501 lbs., the same pressure coming on the right-hand or western rail when travelling in the reverse direction. In more northerly parts the lateral force increases, reaching its maximum at the North Pole, in which region, in a case similar to the preceding, the extra pressure on the right-hand side would be 660 lbs. In the large ocean steamers the force is considerably greater; the side-pressure on the Inman liner "City of New York" being about 936 lbs. The tendency of this lateral pressure would be to drive the vessel (if on a northward or southward course) somewhat to the east, so that to keep on 1 a prescribed course requires a slightly-increased engine power to overcome the tendency to deviation. This increase is, however, not more than 10.000. Such as it is, it is inappreciable on the east and west run between Liverpool and New York; but would be distinctly perceptible in a voyage to Buenos Ayres. P. W. B. The Law of Thermal Radiation. By W. FERREL. (The American Journal of Science, vol. xxx., 1889, p. 3.) => In this Paper the Author compares the formulas of the law of thermal radiation as determined by Dulong and Petit seventy years ago, and Stefan in 1879, and he also examines the experiments of Lehnebach, Rosetti, Schleiermacher, Graetz, Violle, Langley, and others. When H the rate with which heat is radiated by a body from each unit of surface, T = the temperature of the radiating body, m = the value of H at the temperature of T = 0. Then if H =mar when a = 1·0077 the formula expresses Dulong and Petit's law, which, however, is only true for empty space, and requires modification when the body is contained within a perfect enclosure. The Author compares Tables of the results of Dulong and Petit's experiments and Stefan's experiments, and remarks that although their expressions satisfy the rates of cooling equally well from 80° to 240° Centigrade, yet that little reliance can be placed from this fact upon deductions as to the rate of cooling in space. Among other matters the Author mentions Langley's deductions from his experiments at the Edgar Thompson Steelworks, near Pittsburg, that the solar heat radiation is about one hundred times greater than that of melted iron at a temperature of 1,800°, angular area for area. Calculating from this, and making the assumption that molten iron has the same relative radiativity as an equal portion of the solar surface, and correcting in the light of Dulong and Petit's and Stefan's laws, the Author estimates that the solar temperature is probably 5,933° Centigrade. In conclusion, the Author remarks that it is necessary to have radiation experiments made at much lower temperatures than those of any researches yet attempted in order to arrive at the true value of the rate at which heat is radiated from each unit of surface at zero. D. C. INDEX TO THE MINUTES OF PROCEEDINGS, 1889-90.-PART I. "Aberdeen," s.s., trials of the triple-expansion engines of the, 259. Accidents in Mines. See Mining-accidents. Addis, F. H., elected associate member, 150. Address of Sir John Coode, President, on assuming the chair for the first time after his election, 1. Agnew, S. H., elected associate member, 150. Allan, J. F., elected associate member, 150. Allard, E., prevision of floods, 432. Allen, P. R., elected associate member, 150. Alterion Company's electric apparatus for preventing incrustation in boilers, 88. American engineers, visit of the, to Europe, in 1889, 2. Amphlett, E. A., B.E., admitted student, 149. Annealing-furnaces. See Furnaces. Anderson, R. B., elected associate member, 150. R. H., admitted student, 149. Andrews, S. G. T., elected associate member, 150. Aqueduct, Cuneo, cement tubes for the, 412. Armitage, F. R., B.A., admitted student, 149. Armstrong, Sir W. G., and Co., early types of water-tube boilers made by, 121. Bacteria present in the soil, on the number of, 448. Bailey, J. H. D., admitted student, 149. F., elected associate member, 150. Balance-sheet system, first application of the, to engine-trials, 257. Baldwin, L. L., admitted student, 149. Bar, Charleston, U.S., "stone fleet" sunk in the channel over the, 288. Barnett, G. A., C.I.E., elected associate, 151. , W. D., railway workshops, their design and construction, 469. Barrowcliff, G. H., elected associate member, 150. |