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OF THE STATE OF PENNSYLVANIA,
FOR THE PROMOTION OF THE MECHANIC ARTS.
MECHANICAL AND PHYSICAL SCIENCE,
Civil Engineering, the Arts and Manufactures.
PROF. JOHN F. FRAZER,
Assisted by the Committee on Publications of the Franklin Institute.
VOL. 80.-No. 475.
Vol. L.-JULY, 1865.—No. 1.
PUBLISHED BY THE FRANKLIN INSTITUTE AT THEIR HALL.
By B. F. ISHERWOOD, Chief Eng. U. S. Navy:
CHIEF OF THE BUREAU OF STEAM ENGINEERING,
Made principally to aid in ascertaining the comparative economic efficiency of Steam used with different measures of expansion; and the absolute cost of the power obtained therefrom in weights of Fuel and Steam.
The causes and quantities of the condensations in the Cylinder; the economic effect of Steam-jacketing, and Steam superheating, and of various proportions of Cylinder capacity for the same weight of Steam used per stroke of piston.
The economic and absolute evaporative efficiencies of Boiiers of different types and proportions. The comparative calorific values of different Coals as steam generators. The performance of United States War Screw Steamers, &c., &c., &c.
THE WHOLE BEING
Original matter, composed of extensive Experiments made by the
General Problem of Trussed Girders. By DE VOLSON WOOD, Prof. C.E., University of Michigan.
Concluded from page 317, vol. xlix.
In the latter part of the preceding article I found the position of the neutral axis when the resistances of the fibres are directly proportional to their distance from the neutral axis. We will now proceed to find it according to Barlow's theory.
b. Let there be two laws of resistance. According to one let the resistances vary directly as the distance from the neutral axis; and according to the other let the resistance be the same on each unit. 1. Let the moduli of elasticity be equal. Then will the resistances to direct elongation or compression be equal at equal distances from the neutral axis.
Using the notation before given, and we have
resistance of a unit of fibres at a unit's distance from the neutral axis to direct elongation or compression. I speak of DIRECT resistances because the longitudinal shearing is not included.