CHAPTER IV.

MASONRY.

THE Contract for the masonry of the bridge was originally let to Messrs. Vipond and Walker, of Kansas City. On the 1st of July, 1867, Mr. Walker retired from the firm, and his place was supplied by Mr. J. H. Burns; on the 25th of November, in the same year, Mr. Vipond died, and the work under the contract was completed by Mr. Burns.

By the terms of the contract the Company agreed to furnish all derricks required for handling stone, both at the quarries and on the river, and also stone-boats for transporting stone to the pier sites, and the use of their steamboat to tow these boats to the points desired. The contractors were to furnish all smaller tools, to provide power for the derricks, and to keep derricks and boats in repair while in their use. The cement was to be purchased by the Company and charged to the contractor at cost.

The stone used was limestone, the greater part of which was quarried in the bluffs south-west of the city, and within three miles of the bridge site; a quarry was also opened on the north side of the river, from which a portion of the stone used in Piers 5 and 6 was obtained. Several varieties of stone were worked, the best of which was a compact blue limestone, of nearly uniform color, found in continuous layers varying from 15 inches to two feet in thickness. As this stone could not be obtained in large quantities without very expensive stripping, its use was confined to the ashlar work of the upper parts of the piers; the whole of the piers, below the top of the ice-breakers, was built of a more coarsely grained stone, of a white or gray color, which worked into thicker courses than the blue stone, and which was used for backing throughout. The stone was quarried in the summer and early autumn of 1867, so as to allow a sufficient time for seasoning; it was found in general to stand the frost well,

with the exception of one lot of very heavy stones from a single quarry; these were badly broken by the first heavy frost of November in that year, and the products of that quarry were condemned for dimension work above low water.

The specifications required the work to consist of the best description of rock-range work, the face stones to be cut, squared, and bedded with onequarter inch joints, and with the vertical joints cut back at least nine inches. from the face; the ice-breaker faces were to be cut smooth, and drafts cut on all angles; the shoulders and corners were to be trimmed so as to have no projection exceeding one inch and a quarter, while no projection exceeding four inches was to be allowed on any part of the pier. The whole size of the top of each pier was finished smooth, and the stone bush-hammered, the face of the coping being also trimmed almost smooth. The face stones were fastened together by iron cramps of inch round iron, as high as the top of the icebreakers, and this system of dowelling was continued at the shoulders up to the overhanging courses, where it was again extended to the whole face. The backing was formed of heavy uncut stone, laid in full mortar beds, the crevices being filled with smaller stones laid also in mortar. The whole amount of masonry was laid in hydraulic mortar, the usual proportions of the mixture being two parts of sand to one of cement; in the upper courses, which are rarely or never exposed to the water, this mortar was mixed with a paste of fat lime. The hydraulic cement was of the well-known Louisville manufacture, the greater part being purchased from the Falls City Cement Company.

The masonry contract included the beton used and the riprap thrown around the piers, though not the river protection above the bridge. The beton was formed of broken limestone, sand, and cement, the proportions varying with the purpose for which it was used. The stone was broken by hand into pieces that would pass through a three inch ring. The method of preparing the beton for use, was to mix the mortar separately in a grout box, and then pour it with pails over the stone, which had previously been spread evenly over the floor and moistened with water to remove all dirt; the mixture was then rapidly turned over with shovels and deposited at once in its place. If placed at once under water, it was lowered carefully in boxes of the patterns already described. The beton used at Pier No. 3, was formed of six parts of stone to.

three of sand and two of cement, a slightly larger proportion of cement being used in the first few feet. It was found, however, that so large a measure of sand was not favorable to the rapid setting which is important when the beton is exposed to the water from the very first, and in the subsequent foundations this proportion was changed; the beton used at Pier No. 4, consisted of eight parts of stone to two of sand and three of cement; that used at Pier No. 2 had nearly the same constitution. In laying beton under water considerable inconvenience was found from the laitance which formed in large quantities, especially if the mortar had been mixed too thin, or if the water was very cold ; it was sometimes necessary to suspend the work for a day or two, and pump out the laitance, but it was generally found sufficient to pump for a few hours every night, though when working in this manner care had to be taken to avoid washing the beton before it had set.

Both masonry and beton were laid in extremely cold weather, the use of hot sand and water being found to make this perfectly practicable. The sand was heated in large sheet-iron braziers, and the water warmed in cast-iron kettles, one of each being found sufficient to supply the force working on a pier. The heat, which was thus artificially given to the mortar, hastened its setting, causing this to take place before the mass had cooled enough to make freezing possible.

The form of pier adopted is somewhat unique, and was selected from the advantages it was thought to offer in combining a roomy bridge-seat with a slender and graceful pier. The accompanying lithograph, representing Pier No. 1, and taken soon after its completion, shows the general form of the oblong piers.* These piers are built with a side batter of three-quarters of an inch to a foot, or 1 in 16, and the same on the starling; the ice-breakers have a batter of six inches in a foot, or one in two, giving to the cutting edge of the nose a retreat of eight inches and a-half in each vertical foot. The angle made by the two faces of the starling, measured on a horizontal plane, is a right angle. The ice-breakers finish at an elevation of 116, this being considered the greatest height at which the ice will ever move in the river; the height at

The full plans of the several pieces of masonry are given on Plate VII.