Another kind of street improvement which must be considered is macadam. In small towns, and some quite large cities, most of the streets are improved in this way. When well maintained and kept smooth, but not too hard, it forms a most agreeable surface for driving. It should not, in the writer's judgment, be classed as a pavement at all, certainly not as a permanent one, and its use should be restricted to park drives and boulevards (for maintaining which liberal appropriations can be secured), and to suburban roads, where sewers and subsurface pipes have not yet been laid, and where temporary roads are required to furnish convenient communication between centers of population, and to assist in developing these districts.
Macadam has no place in a city street, nor is it wise to lay it on the entire width of a roadway. It best serves its purpose when laid in a comparatively narrow strip, leaving the sides of the road unimproved, except for the formation of earth gutters, so that the surface water can readily soak away where the soil is sufficiently porous.
Macadam is the most expensive of all street surfaces to keep in thoroughly good condition, and in this country it is rarely, if ever, so maintained, except in some of our park roads.
The pavement which is to-day, more generally than any other, superseding stone on all streets where the traffic is not excessive nor the grades extreme, is asphalt. It is scarcely necessary to attempt to give a history of the use of this material, how its adaptability to paving purposes was first discovered by the improved condition of the roads over which it was hauled from the French mines for use in reservoir and tank linings, etc. The drippings from the carts were observed to have been compacted by travel until a smooth, hard roadway resulted. The first street to be paved with it was Rue Bergera, in Paris, in 1854, and it was so successful that in 1858 Rue St. Honore was similarly treated. An asphalt pavement was laid in Threadneedle Street, London, in May, 1869, and in Cheapside and Poultry in the fall of 1870, while in Berlin its use began in 1873.
Eighteenth Avenue, Brooklyn; Macadamized Full Width of Roadway and Gutters paved, with no Provision for Surface Drainage.
The laying of bituminous pavements in this country began in 1869, and they were first made of tar concrete, or Scrimshaw. Asphalt began to be used within the next year or two, and its popularity has been astonishing, as will be seen from the fact that on January 1, 1898, the area of this kind of pavement laid in the United States was, as nearly as could be ascertained, thirty million square yards.
There is a notable difference between the European and American asphalts. The former may be called natural and the latter artificial pavements. In the former the material, as it comes from the mine, is ground to a powder, heated, placed upon the foundation prepared for it, and tamped into approximately the same condition as before it was disturbed, though usually the product of several mines is mixed in order to obtain the best percentage of bitumen, but nothing is added to or taken from the bituminous rock. In the pavement usually laid in America, on the other hand, only a small proportion of the material is brought from the asphalt deposits, the principal part of it (sand) being obtained near at hand. In the one case the cost of long ocean or rail transportation has to be paid on the entire mass forming the pavement, while in the other this expense attaches to but from twelve to fifteen per cent of the material. This, of course, is a great advantage, and at recent prices it is scarcely possible for the European rock asphalts to compete with the artificial ones.
The making of a pavement from one of the standard asphalts may be briefly described as follows: The material as found in Nature has this composition:
| Bitumen | 38.14 | per cent. |
| Organic matter, not bitumen | 7.63 | " |
| Mineral matter | 26.38 | " |
| Water | 27.85 | " |
| ——— | ||
| 100.00 |