572 PRACTICE OF AGRICULTURE. Part III. 



though the circuit should be much greater than that which would be made in crossing 

 the hill. Where a hill has an ascent of no more than one foot in thirty, the thirtieth part 

 of the whole weight of the carriage, of the load, and of the horses, must be lifted up, 

 wliilst they advance thirty feet. In doing this, one thirtieth part of tlie whole load con- 

 tinually resists the horses' draught ; and in drawing a waggon of six tons' weight, a 

 resistance equal to the usual force of two horses must be exerted. 



3551. A perfectly level road is not cdivays the best for every species of draught. Slight 

 and short alternations of rising and falling ground are serviceable to horses moving 

 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 mus- 

 cular powers moderately exercised, one after another ; and this variety lias not the same 

 tendency to fatigue. A perfectly level road, both with respect to its direction and 

 its breadth, is always dirty in wet weather ; because the rain water can neither run off to 

 the side of the road, nor along the ruts. Such roads, therefore, as are level in their line 

 of direction, should always have a fall from the middle to the sides, and should be kept 

 as much as possible free from ruts. 



3552. According to Stevenson, and we believe to all the most scientific road engineers, a level straight 

 road is decidedly the best. He says, " in an uphill draught, a carriage may be conceived as in the state of 

 being continually lifted by increments proportional to its rise or progress upon the road. Every one knows 

 that on a stage of twelve "miles the post-boy generally saves, as it is termed, at least half an hour upon the 

 level road, because on it he never requires to slacken his pace as in going uphill. Now, if he, or his com- 

 pany, would agree to take the same time to the level road that they are obliged to do upon the undulating 

 one, the post-master would find no difficulty in determining which side of the argument was in favour of 

 his cattle. With regard to the fatigues or ease of the horse, Mr. Stevenson upon one occasion submitted 

 the subject to the consideration of a medical friend (Dr. John Barclay of Edinburgh, no less eminent for 

 his knowledge, than successful as a teaclier of the science of comparative anatomy), when the Doctor made 

 the following answer : ' My acquaintance with the muscles by no means enables me to explain how a horse 

 should be more fatigued by travelling on a road uniformly level, than by travelling over a like space upon 

 one that crosses heights and hollows ; but it is demonstrably a false idea, that muscles can alternately rest 

 and come into motion in cases of this kind. The daily practice of ascending heights, it has been said, 

 gives the animal wind, and enlarges his chest. It may also, with equal truth, be affirmed, that many horses 

 lose their wind under this sort of training, and irrecoverably suffer fYom imprudent attempts to induce 

 such a habit' In short, the Doctor ascribes ' much to prejudice originating with the man, continually in 

 quest of variety, rather than the horse, who, consulting only his own ease, seems quite unconscious of 

 Hogarth's Line of Beauty.' " {Report on the Edinburgh Railway.) 



3553. A dry foundation, and 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 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 of 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. 



3554. The ascent of hills, it is observed by Marshal, is the most diflBcult 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 inegular 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. 



