578 PRACTICE OF AGRICULTURE. Part III. 



3587. An artificial road in Britain is only required to obviate the inconvenience of a 

 very unsettled climate. Water, with alternate frost and thaw, are the evils to be guarded 

 against ; consequently, nothing can be more erroneous than providing a reservoir for 

 water under the road, and giving facility to the water to pass through the road into this 

 trench, where it is acted upon by frost to the destruction of the road. As no artificial 

 road can ever be made so good and so useful as the natural soil in a drj/ state, it is only 

 necessary to procure and preserve this dry state of so much ground as is intended to be 

 occupied by a road. 



3588. Tlie first operation in making a road should be the reverse of digging a trench. 

 The road should not be sunk below, but rather raised above, the ordinary level of the 

 adjacent ground ; care should at any rate be taken, that there be a sufficient fall to take 

 off the water, so that it should always be some inches below the level of the ground upon 

 which the road is intended to be placed : this must be done, either by making drains to 

 lower ground ; or if that be not practicable, from the nature of the country, then the soil 

 upon which the road is proposed to be laid must be raised by addition, so as to be some 

 inches above the level of the water. 



3589. Having secured the soil from under-wafer, the road-maker is next to secure it from 

 rain water, by a solid road made of clean dry stone or flint, so selected, prepared, and 

 laid, as to be perfectly impervious to water; and this cannot be effected unless the 

 greatest care be taken that no earth, clay, chalk, or other matter, that will hold or conduct 

 water, be mixed with the broken stone ; which must be so prepared and laid, as to unite 

 with its own angles into a firm, compact, impenetrable body. 



3590. The thickness of such road is immaterial, as to its strength for carrying weight; 

 this object is already obtained by providing a dry surface, over which the road is to be 

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

 if water passes through a road, and fills the native soil, the road, whatever may be its 

 thickness, 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 1 806 ; since which time it has been in contemplation to change the line, and conse- 

 quently it has been suffered 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, nor had the frost affected it during the winter pre- 

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



3591. Several new roads have been constructed on this principle within the last three 

 years. 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 traffic (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. 



3592. Improvement of roads, continues M< Adam, "upon the principle I have endeavoured 

 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 (1819-20); 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." 



3593. On M' Adam's 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 insufficient. He adds, however, 

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

 preparing 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.) 



