A cobble-stone pavement consists of cobble stones or small bowlders placed side by side upon a bed of sand or upon the natural soil. Fig. 136 shows a transverse section of such a pavement. The earliest pavements in many of the older Amer ican cities were of this form, and until recent years on account of their comparatively low first cost were quite common. In 1884, 93 per cent of all the pavements in Philadelphia were made of cobble stones; but in 1901 less than 6 per cent were of this kind. At present Baltimore has 321 miles of cobble-stone pavement,— more than any other city in the United States,—over 90 per cent of the pavements being cobble stones. In September, 1901, New York City still had 229 miles of streets paved with cobble stones, although they are rapidly being replaced with better pavements.
Since the introduction of asphalt and brick pavements, and since the decrease in the cost of stone-block pavement by the introduction of improved methods of quarrying, and since the decrease in the cost of crushed-stone roads by the invention of the machine rock crusher and the steam road-roller, there is little excuse for the con struction of cobble-stone pavements. The construction of such
pavements have been practically abandoned, and in some cities it has been prohibited by law—like theft and murder.
However, because of their historic interest and because yards and alleys, and also gutters and crossings of unpaved streets are still sometimes paved with cobble stones, this form of pavement will be briefly considered. The ordinary European cobble-stone pavement is much superior to that of this country; but with a little care a cobble-stone pavement can be constructed which is much superior to that ordinarily seen in American cities.