4 BULLETIN 220, U. S. DEPARTMENT OF AGEICULTUEE. 



FRENCH CONSTRUCTION PREVIOUS TO 1775 (ROMAN METHOD). 



By the time that road building was revived in France, in the 

 seventeenth century, the Roman methods of road building had been 

 greatly modified, though the Roman form, especially in the founda- 

 tion, was still retained. Under the ministry of Colbert (1660-1669) 

 as controller general of finances, about 15,000 miles of stone roads 

 were built, practically all with an undrained foundation consisting of 

 one or more layers of large flat stones placed in the bottom of a 

 trench-like excavation. These stones were then covered with a thick 

 layer of more or less finely broken stone. As no systematic main- 

 tenance was attempted, the roads rutted badly, and it was only rarely 

 that the broken stone consolidated properly. The total thickness of 

 the roads was from 1J to 2\ feet. 



Plate II, figure 2, illustrates the type of road constructed in France 

 previously to 1775. This type was modeled on the Roman system. 



Section A shows the earth foundation, which was flat. 



Section B represents the first course. This course was composed of 

 flat stones laid by hand in two or more layers. The total width of 

 this course was 18 feet and the depth was from 9 to 10 inches. 



Section C shows the second course, a layer of small stones, which 

 were broken in place with hand hammers. 



Section D shows the finished surface. This course was composed 

 of stones broken by hand into sizes smaller than the underlying 

 material. It was left to be consolidated by traffic. The total thick- 

 ness of the road in the center was from 18 to 20 inches and at the sides 

 from 12 to 14 inches. 



TRESAGUET METHOD. 



About 1775 a form of construction, supplemented by continual 

 maintenance, came into prominence in France. It had long been 

 advocated by Pierre Marie Jerome Tresaguet, a noted French engi- 

 neer. He held that good drainage and systematic maintenance were 

 absolutely necessary for good roads. By providing a properly 

 crowned and drained foundation, he reduced the required thickness 

 more than one-half and provided a better and more serviceable road. 

 The small stones were broken more uniformly and, by a little atten- 

 tion after placing, soon bonded under the traffic. The resulting roads 

 were smooth and afforded comfortable traveling. 



Plate III, figure 1, illustrates the type of road constructed in France 

 by Tresaguet from 1775 to 1830. 



Section A shows the earth foundation shaped parallel to the finished 

 surface. 



Section B represents the first course, which was composed of flat 

 stones laid on edge lengthwise across the road and beaten to an even 

 surface. The depth of this course was about 5 inches. 



