48 



to the former in hardness or tenacity, yet possesses these quali- 

 ties to a sufficient degree not to warrant their being rejected as 

 road material. These stones have gone through the same pro- 

 cess of attrition which has rounded the edges and smoothed 

 the surfaces of the former, and they were submerged for the 

 same period in that flood of water without disintegration. To 

 the eye, no more effect has been produced on one than on 

 the other. If they have been able thus to withstand the effects 

 of the elements and of attrition, they will answer to a certain 

 extent the purpose for which we require them ; in fact, if there 

 were no harder stone, we should consider this very good mate- 

 rial. The same quality of stone to which we have referred 

 may be obtained already broken into the suitable size, from the 

 quarries on the North River. The relative cost of each would 

 decide between them. 



APPLYING THE MATERIAL TO THE ROAD BED. 



In referring to this subject, Professor Mahan states : 

 Broken-Stone Road- Covering. — The ordinary road-covering 

 for common roads, in use in this country and Europe, is 

 formed of a coating of stone broken into small fragments, which 

 is laid either upon the natural soil or upon a paved bottoming 

 of small irregular blocks of stone In England these two sys- 

 tems have their respective partizans, the one claiming the 

 superiority for road-coverings of stone broken into small frag- 

 ments, a method brought into vogue some years since by 

 McAdam, from whom these roads have been termed Macadam- 

 ized / the other being the plan pursued by Mr. Telford in the 

 great national roads constructed in Great Britain within about 

 the same period. 



" The subject of road-making has within the last few years 

 excited renewed interest and discussion among engineers in 

 France ; the conclusion drawn from experience, there generally 

 adopted is, that a covering alone of stone broken into small 

 fragments is sufficient under the heaviest traffic and most fre- 

 quented roads. Some of the French engineers recommend, in 

 very yielding clayey soils, that either a paved bottoming, after 

 Telford's method, be resorted to, or that the soil be well com- 

 pressed at the surface before placing the road covering. 



