S80 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[AUGUSTI 



WOOD PAVING. 



1. On the Use of Mechanical Power in Draught on Turnpike Roads, 

 nilh Refennce to the neiv Si/stem of Wood Paving. London: 

 Blackwood, 1842. 



2. Wood Paving in Loiidon ; a practical Treatise. By J. Lee Ste- 

 vens. London: Spencer, 1S41. 



3. Wood Paving in the Provinces. By the same. 



4. Prospectus of the Marykhone Practical and Scientifc .Association 

 for the Promotion of improved Street Paving. 



Our earliest associations heretofore have taught us, in thinking of 

 great roads as works of art, to esteem durability as their chief excel- 

 lence, and a compact mass of stone as the best means of ensnring 

 this attribute. Talk of engineering monuments, and the Appian Way 

 rises before the mind's eye, or some of those many roads of the 

 Romans which, after centuries of wear and tear, still bear on them 

 the ever-flowing tide of traffic. And now this is to be as a dream ; 

 our ancient prepossessions in favour of stone or a macadamized con- 

 crete are to give way to what has been considered a most perishable 

 material, one rejected in all structures in which the property of 

 durability is to be consulted. We are not totally unacquainted with 

 wooden roads, for the corduroy roads of America have made us 

 familiar with them ; but whatever our ideas may be of their capaljility 

 of holding out against the ravages of time, we have too little liking 

 for them, too little opinion of their comfort, to give them any chance 

 of jolting our successors, when we are able to afford a more costly 

 road. It is, nevertheless, true that the experience of two or three 

 years has been sutficient to establish the efficiency of wood as a 

 paving material, and to ensure it a large future extension. 



Our prepossessions on the subject have been that wood as a paving 

 material would be subject to great abrasion, would rapidly decay 

 under the influence of weather, and would present a very slippery 

 surface. The effect of damp upon wood, however, is rather para- 

 doxical : if partially subjected to damp then decay ensues, but while 

 kept constantly damp the injury is trifling. The abrasion experience 

 has proved to be less than that of granite, while the practical opera- 

 tion, as we shall hereafter show, is such as allays all fears on that 

 ground. As to the slipping of horses, the greater frequency of its 

 occurrence upon wood paving is very questionable, while it is an evil 

 which attaches only to a partial line of wood and stone paving, for 

 were wood used on a large scale, an alteration in the shoes of horses, 

 such as has been well provided by several inventions, would wholly 

 remove this cause of objection. 



Having, therefore, in wood a paving material of sufficient durability, 

 whether we regard resistance to weather, or to abrasion from the 

 weight carried on it, we have now to look at it in operation. In 

 all specimens which have stood well we find an upper layer of wood 

 reposing on a bed of concrete; for as to the idea of dispensing with 

 the underlayer of concrete, it is one the fallacy of which has been 

 shown and abandoned. The concrete we regard, therefore, as an 

 essential feature of the system ; and thus we have a non-elastic 

 stratum of concrete with an elastic covering of wood, or a jacket, as 

 it may be termed, in reference to its operations in defending the con- 

 crete from the weather, and a buffer, as repelling the shocks of the 

 carriages traversing the road. Now it is in these elastic properties 

 that, according to us, the whole secret of the success of wood-pav ng 

 lies. Let us consider that there is not merely the road, which has to be 

 provided for, but also the power which traverses it. Theoretically it 

 might seem that the smoother and consequently the harder and more 

 durable the road the better ; but there is, as we have said, the power 

 using the road to be taken into account, and the difference between an 

 elastic and a non-elastic road is great in this respect. For as in the 

 case of resistance to impact on the part of the non-elastic medium, 

 the whole is distributed through the elastic medium of the 

 power, so to speak, traversing the road, so, in the case of an elastic 

 medium, this resistance is divided, and thus apparently diminished. 

 Familiarly, this is illustrated by the example of wood and stone stairs: 

 while we run up stone stairs our feet are pained, and we get 

 sooner tired, to which the softness of the wooden stairs is an imme- 

 diate relief. Therefore, upon the elastic medium we can do more 

 work, either as to quantity or as to the length of time in which we 

 are employed on it. This is the case with the horse : when it gets 

 on the wood pavement the relief is sensible; instead of the whole 

 resistance from the impact with the stone being communicated to 

 its feet, as in the case of stone, it is distributed. If we consider 

 the structure of the horse's leg, the natural habits of the animal, and 

 the serious effect of a London pavement in shortening its working 

 life, we must feel very sure that, on the ground of comfort to the 



horse alone, the advantages of wood-paving are very great. 

 Indeed, upon some lines of road, where there is much wood pave- 

 ment, the sensible benefit to the omnibus and cab proprietors is 

 acknowledged, and the extension of wood-paving must tend greatly 

 to utilize the power of the horse, and so to reduce the price of his 

 labour under every head, whether of length of life, of health, or of 

 subsistence. Animate power is, nevertheless, not the sole power 

 which we have to consider: a short space of time must bring the 

 steam carriage also on the road, and we must provide for that. But 

 the steam carriage is in a iike manner provided with delicate and 

 elastic machinery, and we know that the effects of vibrations on hard 

 surfaces are greatly to increase the wear and tear and consequent 

 expense of the machine. On this ground, therefore, the wood pave- 

 ment is also to be preferred, in which respect many advocates of the 

 steam carriage system have admitted the superiority of wood. So 

 far, then, as to tlie mere effect of vibration on the elastic power em- 

 ployed, whether animate or inanimate ; but in the case of animals, 

 there is also a voluntary action which, although little regarded, is 

 worthy of some attention. All those who attempt to estimate dynam- 

 ically 'the results of muscular action, are well aware how much the 

 will and disposition, the nervous condition of the animal, has to do with 

 it, and under all circumstances, we should consider that wood would 

 be more favourable to the exertion of the powers of the horse. What 

 the seaman call "working with a will" is half the battle, and those 

 who have noticed the wood pavement in Oxford-street must have 

 seen the evident pleasure which the omnibus and cab horses have in 

 running upon the easier surface. 



In thus considering the tractive power we have perhaps travelled a 

 little out of the logical order, for we should first have considered 

 what is the quality of a wood surface with regard to the degree of 

 resistance it affords to the traffic passing over it. We thought this, 

 however, less important, for the capability of having tight joints is 

 evident, and the smoothness of wood is one of the apparent objec- 

 tions to it. Presenting, therefore, an evident superiority over stone 

 as to surface, the saving in wear and tear of carriages must be con- 

 sequent. Attributing to wood that it causes much less wear and tear 

 than stone to animals or vehicles passing over it, the converse of this 

 is that those animals and vehicles must cause less wear and tear to 

 the road, and, therefore, a very heavy item of expenditure be sensibly 

 diminished, as also the amount of toll levied for the maintenance of 

 the road. We may perhaps here mention that, according to Mr. 

 Macneill's opinion, "based on the relative wear of the iron of horses' 

 shoes and of the tires of the wheels, that the wear and tear of horses' 

 shoes and consequent destruction of the road is much greater than 

 that of wheels, and the injury, consequently, of a steam carriage 

 would be less than that of a coach and horses. While bringing in 

 corollary opinions of this kind, we must not dismiss the question of 

 elasticity without referring to the evidence of Mr. Macadam, as to 

 the good effects of laying over a bog a Macadamized road on an under- 

 layer of hurdles, which is the system of wood-paving reversed. It 

 may, however, suggest some ideas. 



As to the details of wood-paving, we are on the present occasion 

 incurious about them, whether they ought to be cubes or hexagons, or 

 what, provided always that they are laid upon a solid substratum. 

 The mode in which the blocks are laid, as to the grain of the wood, is 

 important to be considered, whether with the fibres vertically, hori- 

 zontally, or diagonally. This is a subject well worthy of experiment, 

 first in relation to the mechanical strength, then as to abrasion of 

 surface, and further as to the beneficial effect or otherwise of the 

 admission of damp by the fibres. Another subject for experiment is 

 as to the durability of wood under several circumstances : first, under 

 alternate wetness and dryness, and secondly, while in such condition, 

 as to the effect of frequent traffic or otherwise. It appears at present 

 that, while bearing considerable traffic, wood will stand exposure to 

 all weathers; while in many other circumstances seemingly more 

 favourable, it is attacked with rot. The cause of this has never been 

 satisfactorily ascertained ; but it remains as the subject of experiment, 

 like the anomalies in iron rails, where, side by side, will be found rusty 

 rails and bright ones, under nearly the same circumstances. 



Looking at wood-paving in its various relations, we come to another 

 topic— the convenience to the public from the sound of the wheels 

 being deadened on the wood pavement. The greater quiet which 

 ensues is much appreciated by the shopkeepers and other residents in 

 large thoroughfares ; but the convenience is not less to the passengers. 

 Those on the footway and those in carriages, besides having freedom 

 from noise, which is a great relief to many, are enabled to converse, 

 which at present, in Clieapside or the Strand, is often impossible. It 

 is on this ground of greater quiet that wood-paving has been already 

 adopted around many churches and public buildings, and its extended 

 use for this purpose will not only benefit the auditories but also the 



