JOURNAL

OF

THE FRANKLIN INSTITUTE

OF THE

State of Pennsylvania,

AND

AMERICAN REPERTORY

OF

MECHANICAL AND PHYSICAL SCIENCE,
CIVIL ENGINEERING, THE ARTS AND MANUFACTURES,

AND OF

AMERICAN AND OTHER PATENTED INVENTIONS.

EDITED

BY THOMAS P. JONES, M. D.,

Mem. of the Am. Philos. Soc.; of the Acad. of Nat. Sci., Philad.; the Am. Acad. of Arts and Sci., Mass
the Nat. Inst. for Promotion of Sci., Washington, &c. &c. &c.

AND

JAMES J. MAPES, A. M.,

Prof. of Chem. and Nat. Philos. in the Nat. Acad. of Design; Hon. Mem. of the Scien. Inst., Brussels
of the Roy. Soc. of St. Petersburg, &c. &c. &c.

JOURNAL

OF

THE FRANKLIN INSTITUTE

OF THE

State of Pennsylvania,

AND

AMERICAN REPERTORY.

JULY, 1842.

Civil Engineering.

FOR THE JOURNAL OF THE FRANKLIN INSTITUTE.

Description of the Wooden Aqueduct carrying the Pennsylvania Canal across the river Alleghany, at Pittsburg; from actual With remarks by JOHN C. TRAUTWINE, Civil

measurement.

Engineer.

This aqueduct was built in the year 1829, by Mr. Lothrop of Pittsburg, at an expense to the State of $104,000. It has two abutments, six piers, of stone, and seven arches of timber, of 150 feet clear span each; the whole length of the aqueduct between the abutments being 1092 feet. The masonry is of cut ashlar, in large courses, with rubble filling. The material is a gray sandstone, rather too soft, in my opinion, for such parts of a structure as are exposed to rapid currents, bringing down heavy fields of ice and drift wood, as is the case with the Alleghany. The piers are seven feet thick on top; they batter one inch to a foot, on the sides; are semi-circular at their downstream ends; and are provided (at least those of them which are exposed to the principal force of the current,) with breakwater starlings, of this shape, up-stream. (This term is frequently applied to such starlings, but I cannot perceive its propriety; the expression savors of tautology.) average height of the piers is about forty feet.

The

The timber of the aqueduct is white pine, with the exception of the chords and the pier-posts, which are of white oak, as being better calculated to resist the great strains that come upon them. I conceive, however, that any precaution of this kind would apply with more

VOL. IV, 3RD SERIES.-No. 1.-JULY, 1842.

1