Book II. DIRECTION OF ROADS. 571 



straight and the level line. The line of perfection, for agricultural purposes, is to 

 be calculated by the time and exertion, jointly considered, which are required to 

 convey a given burthen, with a given power of draught, from station to station. On great 

 public roads, where expedition is a principal object, time alone may be taken as a good 

 criterion. 



3547. According to Slevenson, " although in road-making the line of direction must 

 always be subordinate to the line of draught, yet the former is notwithstanding of 

 importance, both as it regards the safety of the traveller, and the trackage of the load. 

 Independently of the numerous accidents which occur from the sudden collision of 

 carriages travelling at speed upon a tortuous line of road, it were even better to go up a 

 moderate acclivity, than to introduce numerous turns, which, to a certain extent, are not 

 less detrimental to the effective power of the horse, than the uphill draught. Every 

 turn in the road, which ultimately amounts to a right angle, does, in effect, suppose the 

 carriage to have been brought from a state of motion to a state of rest, and from rest to 

 motion again. Turns in a road, where they are unavoidable, ought to be formed on 

 curves of as large a radius as the situation will admit. There ought, in laying out a 

 road, to be a kind of compensating balance between the lines of direction and draught ; 

 and wherever weighty reasons occur for varying the diiect line, such as an acclivity to be 

 avoided, more proper soil to be obtained, the avoiding of valuable property, or the 

 including of a village or town, where such motives present themselves, the judgment 

 of the engineer will, of course, be exercised in varying the line of direction." {Ed. Enc. 

 art. Roads.) 



3548. A regular method ofjinding out tlie true line of road between two stations, where 

 a blank is given, and where there is no other obstruction than what the surface of the 

 ground to be got over presents, is to ascertain, and mark at proper distances, the straight 

 line, which is the only certain guide to the surveyor. If the straight line be found to 

 be ineligible, each mark becomes a rallying point, in searching on either side of it for a 

 better. If two lines of equal facility, and nearly of equal distance from the straiglit line, 

 present themselves, accurate measurements are to determine the choice. If one of the 

 best two lines which the intervening country affords is found to be easier, the other 

 shorter, the ascent and the distance are to be jointly considered ; the exertion and the 

 time required are to be duly weighed. 



3549. The nature of the ground, the source of materials, and the comparative exjiense of 

 forming the road, by two doubtful lines, as well as their comparative exposure, are also 

 to be taken into consideration. Although, in some places, Paterson observes, it maybe 

 of little consequence, either to the traveller or to the public in general, which way the 

 ben dings are turned, provided the level is nearly obtained, yet a great deal may depend 

 upon tliose turns or bendings for the real benefit and advantage of the road. In bend- 

 ing it one way, you may have no metals that will stand any fatigue, unless at a great 

 distance and expense ; while, in turning it the other way, you may have metals of the 

 very best quality in the immediate vicinity. In the one way, too, you may be led over 

 ground of a wet bottom, where, even with twelve or fourteen inches deep of metals, there 

 would be difficulty in keeping a good road ; while, in the other, you may have such a dry 

 bottom, that the road would be much easier upheld with seven or eight inches of metals. 

 So that the track that may appear most eligible to the eye, at first sight, may not always 

 be the one that should be adopted. " A combination of all the requisites I have already 

 mentioned should be studied, as far as possible ; and where these cannot be found all to 

 unite, the one possessing the most of these advantages, and subject to no other material 

 objection, should, of course, be adopted." (Treatise on Roads, p. 19.) 



3550. Roads, Edgeworth observes, shoidd be laid out as nearly as may be in a straight 

 line; but, to follow with this view the mathematical axiom, that a straight line is the 

 shortest that can be drawn between two points, will not succeed in making the most 

 commodious roads : hills must be avoided, towns must be resorted to, and the sudden 

 bends of rivers must be shunned. All these circumstances must be attended to ; there- 

 fore a perfectly straight road cannot often be found of any great length. It may, perhaps, 

 appear surprising, that there is but little difference in the length between a road that has 

 a gentle bend, and one that is in a perfectly straight line. A road ten miles long, and 

 perfectly straight, can scarcely be found any where ; but if such a road could be found, and 

 if it were curved, so as to prevent the eye from seeing further than a quarter of a mile of 

 it, in any one place, the whole road would not be lengthened more than one hundred 

 and fifty yards. It is not proposed to make serpentine roads merely for the entertain- 

 ment of travellers ; but it is intended to point out, that a strict adherence to a straight 

 line is of much less consequence than is usually supposed ; and that it will be frequently 

 advantageous to deviate from the direct line, to avoid inequalities of ground. It is 

 obvious, that, where the arc described by a road going over a hill, is greater than that 

 which is described by going round it, the circuit is preferable ; but it is not known to 

 every overseer, that within certain limits it will be less laborious to go round the hill, 



