Having stated the various kinds of pavement as commonly practised by masons, we proceed to notice several deviations from that practice, which have been much talked of, and partially brought into use. The first we shall describe is the patented improvement of Mr. Abraham H. Chambers, of New Bond street, London ; the object is for paving the horse and carriage-ways of our public streets. Mr. Chambers forms the bed of earth or gravel of the usual figure, which is a slightly elevated arch ; this foundation is to be rendered as firm and solid as possible, by ramming, previous to laying down the stones, which are in form the lower portion of a regular quadrangular pyramid, and are arranged so that the sides of each stone shall overlap those in the next row, as exhibited in perspective in the preceding cut. When they are thus laid uniformly and evenly, with their broadest surfaces or bases downward, a quantity of some of those stone-like cements, of which lime is the basis, or the British puzzolana, is to be poured between the joints, filling them to about one third of their depth : when this has become hard, so as to cement the whole into one solid body, the remaining two-thirds of the interstices are to be filled with broken flints, granite, or other hard materials. On each side of this road way are to be constructed deep brick gutters, for the reception of the water, and the small portion of mud that may he formed ; and midway, between each side and the centre•of the road, lateral trenches are to be dug, to lead, by an oblique descent, into the brick gutters: these trenches are to be filled with broken bricks and stones, and serve as a filter, to convey nothing but the water from the middle of the road into the gutters. The patentee considers that a paved carriage-way, constructed upon this plan, will be extremely durable, and will be kept free from mud and sludge.
The patent triangular pavement is founded (as the inventor states), upon the reciprocal bearing and support of the stones. The pavement is formed of granite, or other hard paving stones, of the ordinary size, and each stone is laid or ranged in such a manner, with reference to the several contiguous stones, as that neither can be displaced the eighth of an inch, by any pressure or percus sion, however great, in the ordinary use of the streets. The stones are not wedges or cubes, but formed as repre sented in the subjoined diagram, each containing a protruding or salient angle on the one side, and an indented or re ceding angle on the opposite side ; the receding angle being formed to receive the salient one. Although the first cost
of a pavement of this kind may be greater than ordinary, its probable greater dura bility will, most likely, more than compensate ; besides, its level symmetry, cleanliness, and solidity of construction, derived by each part from the whole snperficies seem to be advantages attached to this species of pavement.
In Macknamara's patent pavement, the stones are comparatively thin, fiat squares; their upper faces have two of the opposite sides of the quadrangle beveled off to an angle of about forty-five degrees ; and underneath each stone the reverse sides of the quadrangle are beveled off in like manner, so that when laid together in the manner exhibited in the engraving on the next page, they may reciprocally support each other. Fog. 1 represents a plan of a street paved on this system ; . 2 exhibits a vertical section of the same, the roadway stones being 1, 2, 3, 4, 5, (as shown on the plan); 6 6 are the gutter stones ; 7 7, those which abut against the curb. Fig. 3 gives a side view of three entire stones, exhibiting the reverse position of the beveled edges, by which the stones are mutually supported. Fig. 4 represents the opposite sides or edges of the same stones.
" By a careful attention to the figures, it will be seen," says the patentee, " that each and every individual block or stone mutually and reciprocally sup port, and are supported by, each other. This principle will be found to apply throughout, each block or stone being upheld by two adjoining ones, and, m return, mutually supporting others that are made to rest upon it. These blocks may be made of any convenient size ; the principal object to be attended to is to make the bounding lines on the upper surface as perfect as the nature of the stones will admit. I shall here observe, that when blocks are used of large dimensions, it will be proper to groove their surfaces to form a better foot-hold for hones; and in order to identify my invention, and thereby endeavour to prevent any infringement on this patent, that it consists solely in working, cutting, or forming the sides of my blocks or stones, so that they shall make alternately obtuse and acute angles, with the upper surface of the block or stone, which, being done, they may be so arranged or combined, that they will mutually and reciprocally support and preserve each other from the imperfection so generally found in the usual practice of paving."