s.
The other supports of the viaduct are wrought iron trestles on masonry
piers, resting on broad concrete foundations. The pressure on the
material beneath the concrete, which is plastic blue clay of varying
degrees of stiffness mixed with fine sand, is about one ton per square
foot.

The Cuyahoga valley, which the viaduct crosses from bluff to bluff, is
composed mainly of blue clay to a depth of over 150 feet below the
river level. No attempt is made to carry the foundation to the rock.
White oak piles from 50 to 60 feet in length and 10 inches in diameter
at small end are driven for the bridge piers either side of the river
bed, and these are cut off with a circular saw 18 feet below the
surface of the water. Excavation by dredging was made to a depth of 3
feet below where the piles are cut off to allow for the rising of the
clay during the driving of the piles. The piles are spaced about 2
feet 5 inches each way, center to center. The grillage or platform
covering the piles consists of 14 courses of white oak timber, 12
inches by 12 inches, having a few pine timbers interspersed so as to
allow the mass to float during construction. The lower half of the
platform was built on shore, care being taken to keep the lower
surface of the mass of timber out of wind. The upper and lower
surfaces of each timber were dressed in a Daniels planer, and all
pieces in the same course were brought to a uniform thickness. The
timbers in adjacent courses are at right angles to each other. The
lower course is about 58 feet by 22 feet, the top course about 50 by
24 feet, thus allowing four steps of one foot each all around. The
first course of masonry is 48 feet by 21 feet 8 inches; the first
course of battered work is 41 feet 81/2 inches by 16 feet 3 inches. Thus
the area of the platform on the piles is 1,856 square feet, and of the
first batter course of masonry 777.6 square feet, or in the ratio of
2.4 to 1. The height of the masonry is 78 feet above the timber, or
731/2 feet above the water. The number of piles in each foundation is
312. The average load per pile is about 11 tons, and the estimated
pressure per square inch of the timber on the heads of the piles is
about 200 pounds.

To prevent the submersion of the lower courses of masonry during
construction, temporary sides of timber were drift-bolted to the
margin of the upper course of the timber platform, and carried high
enough to be above the surface of the water when the