400 STATE BOAED OF AGEICULTUEE. 



of the ground upon wliicli the road is intcuded to be placed ; this must be done 

 either by making drains to lower the level of the water, or if that be not prac- 

 ticable from tlie nature of the country, then the soil upon which the road is 

 proposed to be laid must be raised by embanking so as to be some inches above 

 the level of the water. Having secured the soil from under water, the road- 

 maker is next to secure it from rain water by a solid road made of clean, dry 

 broken stone or flint (none of the fragments of which to be greater than two 

 inches in diameter), so selected, prepared, and laid as to be 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 stone, 

 which must be so prepared and laid as to unite witli its own angles into a lirm, 

 compact, impenetrable body." 



Another practical road-maker, Mr. Patterson of Montrose, of the same age 

 •iis Mr. AIcAdani, commends the ])rinciples proposed by Mr. McAdam, but 

 objects, as we think Avith reason, to his drainage of three or four inches as being 

 insufficient. 



TELFOED EOADS. 



Again Telford, whose roads to-day are the best that England possesses, laid 

 great stress in all his practical operations upon thorough and complete drainage. 

 His roads are made of layers of broken stone resting upon a sab-j^avement of 

 stone blocks. Telford's specifications for a roadway of 30 feet w'ere as follows : 

 "^Upon the level bed prepared for the road materials a hottom course or layer 

 of stones is to be set by hand in the form of a close, firm pavement. The stones 

 set in the middle of the road are to be seven inches in depth ; at nine feet from 

 the center, five inches ; at twelve from the center, four inches ; and at fifteen 

 from the center, three inches. They are to be set on their broadest edges and 

 lengthwise across the road, and the breadth of the upper edge is not to exceed 

 four inches in any case. All the irregularities of the upper part of the said 

 pavement are to be broken off by the hammer, and all the interstices to be filled 

 with stone chips, firmly wedged or 2^acJced hy hand with a light hammer, so that 

 when the whole pavement is finished there shall be a convexity of four inches 

 in the breadth of fifteen feet from the center. This pavement is to be coated 

 with stone broken as nearly as possible into cubical pieces, whose edges must 

 not exceed 2^ inches in length, and Avhich must be applied in layers over the 

 remainder of the pavement so as to make the whole convexity of the road six 

 inches from the center to the sides of it, the whole to be covered with a depth 

 of one inch and one-half of good clean gravel. 



"The advantages of this system are most striking wdien the natural soil is 

 retentive of moisture, as where it is clay the pavement then acts as an under- 

 drain to carry off the water which may find its way through the broken stone 

 surface. Even on a rock this pavement may be laid with advantage to form a 

 dry floor.'' 



walker's systeji. 



A dry foundation aiid clearing the road from water are two important objects 

 which, according to Walker (minutes of evidence before a committee of the 

 House of Commons, 1819), ought to be kept in view in laying out roads. 'Tor 

 obtaining the first of these objects it is essential that the line for the road be 

 taken so that the foundation can be kept dry, either by avoiding low ground, by 

 raising the surface of the road above the level of the ground on each side of it, 

 or by drawing off the water by means of side drains. The other object, viz.. 



