520 PRACTICE OF AGRICULTURE. Part III. 



placed as a covering or roof, to preserve it in that state : experience having shown, that 

 if water passes through a road, and fill the native soil, the road, whatever may be its thick- 

 ness, loses its support, and goes to pieces. In consequence of an alteration in the line of 

 the turnpike-road, near Rownham-ferry, in the parish of Ashton, near Bristol, it has been 

 necessary to remove the old road. This road was lifted and re-laid very skilfully in 

 1806; since which time it has been in contemplation to change the line, and conse- 

 quently it has been suifered to wear very thin. At present it is not above three inches 

 thick in most places, and in none more than four ; yet on removing the road, it was 

 found that no water had penetrated, non had the frost affected it during the winter preced- 

 ing, and the natural earth beneath the road was found perfectly dry. 



3343. Several new roads have been constructed on this principle within the last three 

 ypars. Part of the great north road from London, by Hoddesdon, in Hertfordshire; 

 two pieces of road on Durdham Down, and at Rownham-ferry, near Bristol ; with 

 several private roads in the eastern part of Sussex. None of these roads exceed six 

 inches in thickness ; and although that on the great north road is subjected to a very 

 heavy traffick (being only fifteen miles distant from London), it has not given way, nor was 

 it affected by the late severe winter (1819-20;; when the roads between that and London 

 became impassable, by breaking up to the bottom, and the mail and other coaches were 

 obliged to reach London by circuitous routes. It is worthy of observation, that these 

 bad roads cost more money per mile for their annual repair, than the original making 

 of this useful new road. 



3344. Improvement of roads, continues M'A., upon the principle I have endeavored to 

 explain, has been rapidly extended during the last four years. It has been carried into 

 effect on various roads, and with every variety of material, in seventeen different counties. 

 These roads being so constructed as to exclude water, consequently none of them broke 

 up during the late severe winter (1819-20j; there was no interruption to travelling, 

 nor any additional expense by the post-office in conveying the mails over them, to the 

 extent of upwards of one thousand miles of road." 



3345. On M^Adarns theory the only practical road-maker who has published his opi- 

 nion, is Paterson, of Montrose. He says {Letters and Communications, ^c. 1822,) 

 ** These certainly ought to be considered as the grand first principles of road-making." 

 He commends M'Adam's reasoning on these principles, but objects, as we think with 

 reason, to his drainage of three or four inches as being insuflficient. He adds, however, that 

 though he considers M'Adam's system as erroneous and defective in draining and pre- 

 paring the road for the materials ; yet in regard to the materials themselves, the method 

 of preparing and putting them on, and keeping the road free from ruts by constant at- 

 tention, has his entire approbation. These principles, however, he adds, " are not new; 

 but have been acted upon before. In regard to small breaking, he certainly has had the 

 merit of carrying that mode to greater extent than any other individual that I have heard 

 of; and the beneficial effects arising from it, have consequently been more extensively 

 seen and experienced." (^Letters on Road-making, p. 49.) 



SuBSECT. 3. Road-making as treated of and practised by various eminent Engineers and 



Surveyors. 



3346. The subject of forming a road may be considered as to breadth, drainage, 

 fences, base of the hard materials or artificial stratum, upper line of the stratum, com- 

 position of the stratum, size of the materials, laying, and compressing. 



3347. With respect to breadth the site of every public road, according to Marshal, 

 ought to be sufficiently ample to admit of its division into three travelable lines, namely, 



1. A middle road of hard materials, for carriages and horses in winter and wet seasons; 



2. A soft road, formed with the natural materials of the site, to be used in dry weather, 

 to save the unnecessary wear of the hard road, and to favor the feet of travelling animals; 

 as well as for the safety, ease, and pleasantness of travelling in the summer season ; and 



3. A commodious path, for the vise of foot passengers, at all seasons. There are few 

 roads, even in the environs of populous towns, so public as to require a hard road of 

 more than two statute poles (thirty-three feet) in breadth ; and every public road 

 ought, under ordinary circumstances, to have a line which is travelable at any season, and 

 of ample width to permit two carriages to pass each other, with freedom and safety. 

 This ample width let us set down at one statute pole. In deep clayey districts, where 

 hard materials are difficult to be procured, a single road, of half a pole in breadth, with 

 dilations at proper distances, to let carriages pass each other, may, in many recluse situ- 

 ations,^ be advisable. 



3348. Seventy feet in width seems to be considered by Farey, Walker, Telford, and 

 jnost engineers, as sufficient near the largest towns, and in the case of the metropolis and 

 some others, they consider that ten or twenty feet in width may be paved. The London 

 Commercial road, executed under the direction of Walker, is seventy feet wide ; ten 

 j'eet on each side are occupied as footpaths, twenty feet in the centre is paved for heavy 



