514 PRACTICE OF AGRICULTURE. Part III. 



swiftly ; the horses have time to rest their lungs, and different muscles : and of this 

 experienced drivers know well how to take advantage. Marshal concurs in this opinion, 

 and also Walker, Telford, and most engineers ; and Paterson considers that it would not 

 be proper to line a road upon a perfect level, even to the length of one mile together, 

 although it could be quite easily obtained. It is a fact, he says, well known to most people, 

 at least every driver of loaded carriages knows by experience, that where a horse, dragging 

 a load over a long stretch of road, quite level, will be exhausted with fatigue ; the same 

 length of a road, having here a gentle acclivity, and there a declivity, will not fatigue the 

 animal so much. This is easily accounted for. On a road quite level, the draught is 

 always the same, without any relaxation : but on a gentle ascent, one of his powers is 

 called into exercise ; on the descent, another of his powers is called into action, and he 

 rests from the exercise of the former. Thus are his different muscular powers moderately 

 exercised, one after another ; and this variety has not the same tendency to fatigue. 



3306. A dry foundation and clearing the road from water, are two jmportant objects 

 which, according to Walker {^Minutes of Evidence before a Committee of the House of 

 Commons, 1819), ought to be kept in view in lining out roads. " For 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. that of clearing the road of water, is best secured by 

 selecting a course for the road which is not horizontally level, so that the surface of the 

 road may in its longitudinal section, form in some degree an inclined plane ; and when 

 this cannot be obtained, owing to the extreme flatness of the country, an artificial incli- 

 nation may generally be made. When a road is so formed, every wheel-track that is 

 made, being in the line of the inclination, becomes a channel for carrying off the water, 

 much more effectually than can be done by a curvature in the cross section or rise in the 

 middle of the road, without the danger, or other disadvantages which necessarily attend 

 the rounding a road much in the middle. I consider a fall of about one inch and a half 

 in ten feet, to be a minimum in this case, if it is attainable without a great deal of extra 

 expense. 



3307. The ascent of hillsy it is observed by Marshal, is the most difficult part of laying 

 out roads. According to theory, he says, an inclined plane of easy ascent is proper ; 

 but as the moving power on this plane is " neither purely mechanical, nor in a sufficient 

 degree rational, but an irregular compound of these two qualities, the nature and habits 

 of this power" require a varied inclined plane, or one not a uniform descent, but with 

 levels or other proper places for rests. According to the road act the ascent or descent 

 should not exceed the rate or proportion of one foot in height to thirty-five feet of the 

 length thereof, if the same be practicable, without causing a great increase of distance. 



3308. As precedents for roads through hilly countries, Telford {Minutes before the 

 Committee of the House of Commons, ^c. 1819,) refers to those which he has lately 

 made through the most difficult and precipitous districts of North Wales. " The 

 longitudinal inclinations are in general less than one in thirty ; in one instance 

 for a considerable distance there was no avoiding one in twenty-two, and in 

 another, for about two hundred yards, one in seventeen ; but in these two cases, the 

 surface of the road-way being made peculiarly smooth and hard, no inconvenience is 

 experienced by wheeled carriages. On flat ground the breadth of the road-way is 

 thirty-two feet ; where there is side cutting not exceeding three feet, the breadth is 

 twenty-eight, and along any steep ground and precipices, it is twenty-two, all clear 

 within the fences ; the sides are protected by stone walls, breast and retaining walls and 

 parapets ; great pains have been bestowed on the cross drains, also the draining the 

 ground, and likewise in constructing firm and substantial foundations for the metalled 

 part of the roadway." 



3309. The road between Capel Cerig and Lord PenryrCs slate quarries, may also be 

 adduced as an example of a very perfect enclosed plain in which the ascent is accurately 

 divided on the whole space. 



3310. Cutting through low hills to obtain a level, is recommended by some, who, as 

 Paterson observes, will argue, " that where the hill of ascent is not very long, it is 

 better, in that case, to cut through it in a straight line, and embank over the hollow 

 ground on each side, than to wind along the foot of it. This, however, should only be 

 done where the cutting is very little indeed, and an embankment absolutely necessary. 

 Few people, except those who are well acquainted, are aware of the great expense of 

 cutting and embanking ; and the more any one becomes acquainted with road-making, 

 the more, it may be presumed, will he endeavor to avoid those levels on the straight 

 line that are obtained only by cutting and embanking, and will either follow the level 

 on the curved line round the hill ; or where this is impracticable, will ascend the hill, and 

 go over it by various windings, avoiding always abrupt or sudden turnings." {Treatise, 

 ^c.p.l5.) 



