EARTH, SAND-CLAY, AND GRAVEL ROADS. 35 



which are constructed of such soil, and it happens occasionally that 

 for a considerable distance along a road the soil contains just the 

 proper proportions of sand and clay to produce an excellent road 

 surface for moderate traffic under all weather conditions to which the 

 road is subjected. But, in general, such soils occur only for limited 

 distances, and to secure a continuous surface of this kind, the neces- 

 sary material must be hauled to the road, spread, and compacted 

 after the grading is completed otherwise. More generally, perhaps, 

 the soil composing the roadbed is deficient in only one of the neces- 

 sary constituents, sand or clay, and it frequently m&j be economical 

 to construct the surface by supplying the necessary sand or clay 

 and mixing it with the natural soil of the roadbed, rather than to pro- 

 vide a surface of natural sand-clay material. It may happen, also, 

 that the roadbed contains no material suitable for use in constructing 

 the surface, and that sand and clay are more readily available sepa- 

 rately than ready mixed. In such case both materials may be hauled 

 to the road and mixed in place to form the surface. 



In order to distinguish between common earth roads, which are 

 constructed wholly of the natural soil as it occurs along the road, and 

 those which have been surfaced with especially selected or especially 

 prepared earth which contains sand and clay mixed in such propor- 

 tions as to increase the resistance to wear of the surface as described 

 above, the latter are designated sand-clay roads. This designation 

 evidently includes most of the so-called " topsoil " roads, because 

 topsoil which is especially suited for use in road surfaces generally 

 possesses that quality by virtue of the sand and clay which it 

 contains. 



The sand-clay method of construction has produced its best results 

 in the Southern States, where deep freezing is not a serious factor 

 and where materials suitable for such construction probably are more 

 widely distributed than in any other section of the country. There 

 are many sand-clay roads in the South Atlantic and Gulf States 

 over which heavy loads of cotton and other farm products are hauled 

 throughout the year and which remain continuously in good condi- 

 tion with a comparatively very small outlay for maintenance. And 

 there are innumerable cases where sand-clay surfaces, constructed 

 of even rather inferior materials, have so improved intolerable 

 stretches of sandy or muddy road as to provide for at least fairly 

 comfortable travel throughout the year. Examples of the latter 

 kind are by no means peculiar to the Southern States, but are to 

 be found in nearly every section of the country. Table 7 shows the 

 mileage of sand-clay roads in several representative States for 1909 

 and 1914, respectively, and illustrates how the popularity of this 

 type of construction is increasing. 



