so used, the spaces left between the stones should not be less than six inches, in order that proper ramming can be obtained. No extra compensation shall be paid to the contractor for the use of such concrete, the cost of which is to be included in the price herein stipulated for the masonry in connection with which it is used.

The exposed faces of the main wing wall, of road culverts, of some of the walls and of any other rubble work that the engineer may designate, are to be made of broken ashlar with joints not exceeding one half inch in thickness; the stones not to be less than 24 inches deep from the face, and to present frequent headers. This face work to be equal in quality and appearance to the face of the breast wall in front of the new gate house at Croton dam (Section 1), and to be well pointed with Portland cement. This face work is to be paid for by the square foot of the superficial area for which it is ordered, in addition to the price paid per cubic yard of rubble stone masonry.

Block stone masonry is to be composed mainly of large blocks and is to be used for the steps of the overfall or for other steps, or whenever and wherever ordered by the engineer. It is to be laid in Portland cement mortar, well pointed, or may be ordered laid dry at the price stipulated in clause O, item (o).

This stone, which is to receive the shock of water and ice, is to be especially sound, hard and compact, and of a durable character; it is to be prepared to the dimensions given so that no joint will in any place be more than one inch wide. outside arrises must be pitched to a true line.

The

The outer faces of the masonry dam and of its gate chambers, of the overflow (except steps), and of any other piece of masonry that may be designated, are to be made of range stones, as shown on the plans, the stone to be of unobjectionable quality, sound and durable, free from all seams, discoloration and other defects, and of such kind as shall be approved by the engineer.

All beds, builds and joints are to be cut true to a depth of not more than 4 inches, and not less than 3 inches from the faces to surfaces allowing of one half inch joints at most; the joints for the remaining part of the stones not to exceed two inches in thickness at any point.

All cut arrises to be true, well defined and sharp.

Where this class of masonry joins with granite dimension stone masonry the courses must correspond, and the joining with arches and other dimension stone masonry must be accurate and workmanlike.

Each course to be composed of two stretchers and one header alternately, the stretchers not to be less than 3 feet long

nor more than 7 feet long, and the headers of each successive course to alternate approximately in vertical position.

The rise of the courses may vary from bottom to top from 30 inches to 15 inches in approximate vertical progression, and the width of bed of the stretchers is not to be at any point less than 28 inches. The headers are not to be less than 4 feet in length.

This class of masonry, for the faces of the dam and gate chamber, including the headers, is to be estimated at 30 inches thick throughout. At other places that may be designed by the Engineer, the size of the stones is to be established by him, and the facing stone masonry is to be estimated according to the lines ordered or shown on the plans. In no case are the tails of the headers to be estimated.

The work to be equal in quality and appearance to the facing stone masonry work built by the aqueduct commissioners for their masonry dam across the east branch of the Croton River near Brewster.

All copings that may be ordered and the heads of the arches of the highway culverts, will be classed as facing stone

masonry.

The price herein stipulated for facing stone masonry is to cover the cost of pointing, of cutting chisel drafts at all corners of the gate-house dam and other corners, and of preparing the rock faces; but if any six-cut or rough-pointed work is ordered in connection with this class of masonry it shall be paid for at he prices therein stipulated for such work.

The face bond must not show less than 12 inches lap, unless otherwise permitted.

The pointing of the faces to be thoroughly made with pure Portland cement after the whole structure is completed; unless otherwise permitted, every joint to be raked out therefor to a depth of at least two inches, and, if the engineer is satisfied that the pointing at any place is not properly made, it must be taken out and made over again.

Granite dimension stone masonry must be made of firstclass granite of uniform color, free from all seams, discoloration and other defects, and satisfactory to the chief engineer.

It is to be used for the gate openings in the gate chamber, for the coping of the dam, for the gate-house superstructures and for the crest and first step of the overflow, and at any other place that may be designated by the engineer.

The stones shall be cut to exact dimensions, and all angles and arrises shall be true, well defined and sharp.

All beds, builds and joints are to be dressed, for the full depth of the stone, to surfaces, allowing of one quarter (4) inch joint at most. No plug hole of more than 6 inches across

or nearer than 3 inches from an arris is to be allowed, and in no case must the aggregate area of the plug-hole in any one joint exceed onequarter of its whole area.

The stone shall be laid with one quarter (4) inch joints, and all face joints shall be pointed with mortar made of clear Portland cement, applied before its first setting. All joints to be raked out to a depth of two inches before pointing.

The pointing of all masonry, including the faces of the main body of the dam and of the center walls which are below the ground, is to be done thoroughly with Portland cement mortar, mixed clear where used for all exposed faces of brick and cut stone masonry of all kinds (including the rubble facing); and mixed for other work in such proportion as the engineer shall determine. The cost of all pointing is to be included in the price stipulated for the masonry to which it is applied.

The exposed faces of the cut stone are to be finished in various ways, in accordance with the various positions in which they are placed. They shall be either left with a rock or quarry face, rough-pointed, or fine hammered (six-cut work).

The various classes of face dressing must be equal in quality and appearance to those on the sample in the office of the chief engineer.

In rock face work the arrises of the stones inclosing the rock face must be pitched to true lines; the face projections to be bold, and from 3 to 5 inches beyond the arrises. The angles of all walls on structures having rock faces are to be defined by a chisel draft not less than 11⁄2 inches wide on each face.

In rough-pointed work, the stones shall at all points be full to the true plane of the face, and at no point shall project beyond more than 4 inch, the arrises to be sharp and well defined. Each stone to have its arrises well defined by a chisel draft, which is included in the price for rough-pointed dressing.

In fine hammered work the face of the stones must be brought to a true plane and fine dressed, with a hammer having six blades to the inch.

In measuring cut stone masonry, when the stones are not rectangular, the dimensions taken for each stone will be those of a rectangular, cubical form which will just inclose the neat lines of the same. The price herein stipulated for granite dimension stone masonry is to cover the cost of preparing the rock faces, of making the chisel drafts, and of preparing all holes and recesses and grooves.

No payment will be made for cutting grooves and recesses other than the price paid for the dressing of their surfaces, which are to be fine hammered.

For rough-pointed and fine hammered (six-cut) dressing, a price per square foot of dressing will be paid in addition to the price per cubic yard of masonry, viz. :

For rough-pointed dressing, the price stipulated in clause O, item (t), and for fine hammered (six-cut) dressing, the price stipulated in clause O, item (s).

The exposed parts of the cut stone are generally to be prepared with rock face.

The inside surfaces and copings are generally to be rough-pointed.

All the gateways, grooves, sills, floors, and all other surfaces designated by the engineer are to be fine hammered.

A. F.

132. Specification for First-class Bridge Masonry. The following specification for first-class bridge masonry represents the current practice of one of the leading American engineers:

Masonry-The stone to be used shall be the best quality of limestone from the quarries, except the nose stones for the curved upstream starlings of Piers I, II and III, one stone to each course shall be granite.

The stone must be strong, compact and of uniform quality and appearance and free from any defects which in the judg ment of the engineer may impair its strength or durability.

No course shall be less than 16 inches in thickness and no course, except the coping, shall be thicker than the one beneath it.

Each bed of every stone shall measure at least thirty-six inches in each direction, except that where the thickness of the course is less than twenty-four inches the bed need not exceed one and one half times the thickness of the stone.

The bottom bed shall always be the full size of the stone and no stone shall have an overhanging top bed.

Stretchers shall not be less than four feet nor more than seven feet long and stretchers of the same width shall not be placed together vertically, but this shall not apply to the ends of stretchers where headers come centrally between stretchers.

Headers shall be at least four feet long and shall be at least three quarters their full width for the whole length. There shall be at least two headers on each side of every course between the shoulders.

At least two stones on one side of each course shall reach through to the stone on the other side.

The joints of the face stones shall be cut twelve inches back from the face.

The beds and the joints shall be cut to within one quarter of an inch of a true plane. The depressions below this plane shall not be more than one tenth of the whole surface.

The vertical joints shall not average more than three eighths of an inch and shall not exceed one half. Thin horizontal mortar joints will not be insisted on, but every stone shall be set in a full bed of mortar and brought to a proper bearing with wooden mauls, no levelers being allowed.

All stones must be carefully cleaned and wet before setting, and no mortar beds shall be laid until the course below has been cleaned and wet.

The beds and joints of all face stones shall be cut to true pitch lines.

The face of the upstream cutwaters of Piers I and II shall be fine pointed work with no projections exceeding one half inch.

The coping shall be two feet thick with a bush-hammerep face throughout and be cut with a wash as shown on the plans. A four inch draft line shall be cut on all vertical angles. All other portions of the piers shall have a rough quarry face with no projections exceeding three inches, the quarry face to average at least one and one half inches from the pitch line of the joints and never be run back of such pitch line.

No grab holes shall be made in the face of the coping or on the pointed work of the cutwater.

The stones of the curved upstream starlings of Piers II and III shall be doweled into those of the course below with one and one eighth inch steel dowels extending six inches into each course, these dowels to be placed about ten inches back from the face and seven inches on each side of each joint. The stones of the upper course shall be drilled through before setting after which the hole shall be extended six inches into the

lower course, a small quantity of mortar shall be put into the t

hole, the dowel dropped in and the hole filled with mortar and well rammed.

The coping shall be cut with close joints throughout the whole pier and each stone under the bridge seat shall go completely across the pier.

The joints in the two courses below the coping in all piers shall be cramped with cramps of one inch round iron, sixteen † inches long, the ends four inches into each stone.

The backing shall be composed of stones of the same thickness as the face stones and with beds cut in the same manner as required for the face stones. The spaces between the large stones shall not occupy more than one fifth of the entire area of the pier inside of the face stones and these spaces shall be filled with good rubble masonry carefully laid up on full mortar beds and well rammed.