THE FRANKLIN INSTITUTE,

State of Pennsylvania,-

PROMOTION OF THE MECHANIC ARTS.

MECHANICAL AND PHYSICAL SCIENCE, CIVIL ENGINEERING, THE ARTS
AND MANUFACTURES, AND THE RECORDING OF AMERICAN
AND OTHER PATENTED INVENTIONS.

Reporter of American Patents,

C. M. KELLER, late Examiner, Patent Office, Washington.

THIRD SERIES.

VOL. XVI.

WHOLE NO. VOL. XLVI.

C PHILADELPHIA:

PUBLISHED BY THE FRANKLIN INSTITUTE, AT THEIR HALL.

JOURNAL

OF

THE FRANKLIN INSTITUTE

OF THE STATE OF PENNSYLVANIA

FOR THE

PROMOTION OF THE MECHANIC ARTS.

JULY, 1848.

CIVIL ENGINEERING.

Strength of Materials for Railway Bridges.

The president of the Royal Scottish Society of Arts, (G. Buchanan, Esq.,) at the request of the council, presented an important communication, at their last meeting, entitled "An Exposition on the Strength of Materials, particularly, Cast Iron and Malleable Iron, and their Application in the Construction of Railway Bridges."

Mr. Buchanan commenced by stating, that he did not profess to communicate anything original, but would be happy if he could only draw from the stores of information which had of late years been accumulating on this subject under the hands of very eminent, scientific, and practica! men, such leading facts and maxims as might prove a sure guide for our practice; and such truths, when they become known and established on the unerring grounds of experiment and calculation, could not, he thought, be too widely disseminated. The various strains might all be reduced to two kinds, according as the material is either distended or compressed by any force or pressure. From these two all others arise, and either consist or are compounded of them.The tensile strain is the simplest of all, depending neither on the peculiar form of the materials, nor even on the length, but only on a single element-namely, the section of fracture. This peculiarity of the tensile force was explained and illustrated. In regard to cast iron, the result of the extensive and interesting experiments of Messrs. Hodgkinson and Fairbairn was given; and it was found from the mean of 16 different trials of English, Welsh, and Scotch iron, both hot and cold blast, that this material will sustain about 7 tons per square inch before breaking, the weakest specimen being 6, and the strongest 94. VOL. XVI, 3RD SERIES.—No. 1.—JULY, 1848.