by ramming, when a plank should be laid on the surface parallel to the curb-lines, and the pavement rammed by striking the plank with an iron rammer. If the planking is used crosswise of the street, the pavement is liable to be rammed unevenly. The principles laid down in the stone pavement for the position of the bricks and direction of the courses, both between streets and at intersections, are perfectly applicable to brick. The method shown in Fig. 57, called the herringbone plan, is sometimes used. This, however, is not desirable, as between the streets it brings the line of cross-joints lengthwise to the travel of the street, which permits a weak spot in the pavement, and at intersections it brings a great many of the brick lengthwise of the traffic turning the corners. This method has never been used to any great extent. Brick pavements, especially wlien laid with a sand filler, generally show considerable wear during the first few weeks, especially if laid with rectangular bricks rather than those with rounded edges. This is because the traffic quickly finds any inequalities in the surface, and also because the horses' shoes soon round off the edges of the softer brick; but in a short time this abnormal wear ceases, and from then on the observable wear is slight.

Brick specifications vary principally in the tests that shall be required, joint-filling, and foundations. The following is taken from the specifications of St. Louis:

"To secure uniformity in bricks of approved manufacture, delivered for use, the following tests shall be made:

"1. They shall show a modulus of rupture in cross-breaking of not less than twenty-five hundred pounds per square inch.

"2. Specimen bricks shall be placed in the machine known as a rattler,' twenty-eight inches in diameter, making thirty revolutions per minute. The number of revolutions for a standard test shall be eighteen hundred, and if the loss of weight by abrasion or impact during such test shall exceed thirty per cent of the original weight of the bricks tested, then the bricks shall be rejected. An official test to be the average of two of the above tests.

"No bid contemplating the use of rejected brick shall be entertained.

"Samples may be submitted by manufacturers, in which case

the bidder proposing to use brick of such manufacture will not be required to submit samples. The quality of brick furnished must conform to the samples presented by the manufacturers and kept in the office of the Street Commissioner.

"The Street Commissioner reserves the right to reject any and all bricks which, in his opinion, do not conform to the above specifications.

"Any brick may have a proper shrinkage, but shall not differ materially in size from the accepted samples of the same make, nor shall they differ greatly in color from the natural color of the well-burned brick of its class and manufacture.

"No bats or broken bricks shall be used except at the curbs, where nothing less than half a brick shall be used to break joints. The bricks to be laid in straight lines, and all joints broken by a lap of at least two inches, to be set on edge on the sand as closely and compactly as possible and at right angles with the line of the curb, except at street-intersections, where they are to be laid as the Street Commissioner may direct.

"The pavement to be thoroughly rammed two or three times with a paver's rammer weighing not less than seventy-five pounds. The pavement to be surfaced up by using a long straight-edge and by a thorough rolling of the pavement with a road-roller weighing not less than three nor more than six tons, and when completed to conform to the true grade and cross-section of the roadway.

"All joints in the pavement shall be completely filled with Portland-cement grout. The cement to be of brand approved by Street Commissioner, to be fine ground; eighty-five per cent shall pass through a sieve having ten thousand meshes to the square inch. All cement shall be capable of withstanding a tensile strain of five hundred pounds per square inch of section, when mixed neat, made into briquettes and exposed twenty-four hours in air and six days under water. All cement shall be put up in wellmade barrels, and all short weight or damaged barrels will be rejected. Cement without manufacturers' brand and other certificate will be rejected without test."

"The grout shall be mixed in portable boxes in the proportion of one part cement to one part sand. The cement and sand to be

thoroughly mixed together dry, then sufficient water to be added to make a grout of proper fluidity when thoroughly stirred.

"The grout shall be transferred to the pavement in handscoops, or as the Street Commissioner may direct, and rapidly swept into the joints of the pavement with proper brooms.

"Teams, carts, and wagon traffic and wheeling in barrows, except on plank, will not be allowed on the pavement for at least seven days after the grout is applied.

"The surface of the pavement, when completed, shall be covered with one-half inch of clean, coarse sand of approved quality, which, with all dirt, shall be removed from the pavement and sewer-inlets, by or at the expense of the contractor, at such time, before the final acceptance of the work, as the Street Commissioner may direct."

The following are extracts from the Philadelphia specifications: "The bricks or blocks must be set vertically on edge in close contact with each other, in straight rows across the street excepting at intersections, which shall be paved at an angle of forty-five degrees to the lines of the intersecting roadways, and those in adjoining rows so set as to regularly break joints. No bats or broken bricks or blocks can be used except at curbs, where half-bricks or blocks must be used to break joints. The bricks or blocks, having been set, must be rolled with the above-mentioned steam-roller.

"After being rolled, the surface of the roadway must be true to grade, and show no continuous lines of unequal settlements produced by the roller.

"After being thoroughly rolled, the bricks or blocks shall be grouted with Portland-cement grouting until the joints are filled flush with the surface of the bricks or blocks. The grouting to be composed of one part fresh-ground Portland cement and one part clean bar sand, and mixed with clean water to a consistency that will readily permeate the joints between the bricks."

While brick pavements have been in use in this country for only about twenty years, according to the bulletin of the Department of Labor issued in 1899 there were 18,665,000 square yards in cities having over thirty thousand inhabitants, Philadelphia having the most, with 1,777,123 square yards, Des Moines, Ia., being next, with 1,509,195 square yards, Columbus, O., third, with

1,505,015 square yards, Cleveland, O., with 800,000 square yards, and Louisville, Ky., with 659,733 square yards.

The following are the lowest bids received for brick pavements at different places in the spring of 1900:

CHAPTER X.

WOOD PAVEMENTS.

WITHOUT doubt the crudest and probably the earliest form of a wooden roadway was that which is generally known as the corduroy road. This was constructed roughly by laying logs cut to the desired length across the roadway in close contact with each other. This construction was used at low places in roads across swamps, and, while being very rough and uncomfortable, was fairly serviceable and made many of the roads passable which, without this, could not have been used for a considerable portion of the year. This form of roadway is in use now to a limited extent on wood roads in certain parts of New England.

In Alpena, Mich., roadways, and even entire streets, have been graded with sawdust, while in other parts of the State roads have been constructed of charcoal. The method was to pile logs along the road two or three feet high, and burn them in practically the position in which the material was to be used. After the coal was burned, it was raken off and graded down to the required width and depth of the road. This construction gave very good satisfaction, and in 1845 the Commissioner of Patents in his report stated that at the season when the mud in an adjoining road was half-axletree deep, on the coal road there was none at all, and the impress of the feet of horses passing rapidly over it was like that made on hard-washed sand as the surf recedes on the shore of a lake.

Russia, however, is reported to have had the first real wooden pavements, as hexagonal blocks are said to have been in use there several hundred years ago. They could not have been used to any great extent or for any great length of time, as no detailed record is obtainable of them.

In London, Eng., the first wooden pavement was laid in 1839.