Concrete has also been employed as a foundation with great success, but it is very expensive, and is seldom used except under streets paved with either granite, wood, or asphalte, of which I shall speak hereafter; for if the traffic was so great as to necessitate the use of concrete for a foundation it would surely be better to give the roadway a more durable surface than macadam. The following tables, showing the thickness of the foundation and metalling of broken stone roads, is from a paper on roadways, read to the Association of Municipal and Sanitary Engineers, by Mr. James Hall, Borough Surveyor of Stockton, and may be of use to those who would like to know what proportions to use. -------------+-------------------------+---------------+------------ | Pinned Foundations. | Broken Stones.| Concrete. +--------+---------+------+-------+-------+-----+------ |Pinning.|Covering.|Metal.| Under.| Upper.| Con-|Metal. | | | | | |crete| -------------+--------+---------+------+-------+-------+-----+------ | in. | in. | in. | in. | in. | in. | in. Country roads| 6 | 3 | 4 | 9 | 4 | 4 | 3 Suburban „ | 9 | 3 | 5 | 9 | 6 | 6 | 5 Town streets | 9 | 6 | 5 | 15 | 6 | 10 | 5 -------------+--------+---------+------+-------+-------+-----+------ Chalk has sometimes been used for the bottom of a roadway, but where this is likely to be affected by frost it is the worst material that can be used, as it is likely to blow up the roadway. With regard to the annual outlay upon macadamised roadways, the following comparative tables[20] prepared by Mr. Ellice Clark, the then Surveyor of Derby, may be of interest.