Page:Popular Science Monthly Volume 56.djvu/542

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526
POPULAR SCIENCE MONTHLY.

Good roadways are cheap at any cost, and bad ones are so disastrously expensive that only a very rich country, like the United States, can afford them."

Space will not permit even a brief history of street paving, or an attempt to sketch its development, but reference will be made to the different kinds in general use, PSM V56 D0542 Old roman pavement on a street in pompeii.pngA Street in Pompeii, showing Old Roman Pavement. and the kind most in favor in various cities. Probably no one has introduced the subject of pavements without reference to the Roman roads.

While Carthage was probably the first city to boast of paved streets, the Romans soon followed its example, and all over Europe, Asia, and Africa, as far as the domain of their emperors extended, they built with the greatest care and at enormous expense that magnificent system of roads which were often supposed, in the middle ages, to be of supernatural origin, and remain the wonder of our modern civilization. These roads were generally from four to six metres in width, and were constructed in this way: The roadbed was excavated; in it was placed a layer of stones, which were sometimes united with mortar. These stones were such as were most available, sometimes rounded stones similar to the cobblestones with which we are familiar, and in some cases in the Alps the foundation was a compact mass of angular stones, two feet or more in their longest dimension, carefully fitted together.

On this foundation was placed a layer of plaster made of stone or brick pounded with mortar; then a course of sand and lime or sand and clay, leveled and pounded until very hard. The top or wearing surface was made of irregular flat stones, fitted together with nicety and united with cement. The total depth of these roads, or pavements, as they can properly be called, was from three to (in some cases) seven feet. It is said that in the province of Hispania alone (Spain and Portugal) twenty thousand miles of roads were built.

The first stone pavements to be laid in modern city streets were