work and maintaining it better. He had had referred to certain roadways of been struck on a recent visit to Paris, asphalt with granite channels. It apwith the condition in which some of the peared to Mr. Harrison that granite chanroads had been allowed to get. He be- nels were superfluous. As between an lieved that it had partly arisen from the asphalt roadway with a granite channel, system there adopted of requiring the and a granite roadway with an asphalt contractor to take up every year, whe- channel, qua channel asphalt would be ther it was required or not, one-fifteenth the preferable material. The Val de of the work laid down, which he re- Travers Company had laid a great many garded as a premium on bad work. An- footpaths in England, both in mastic and other reason was the use of lime con- in compressed asphalt, and he was of crete with lime mortar on the top. The opinion that it was not desirable to have only failure that he knew in Val de Travers roadways had been in connection with the use of lime concrete under lime mortar in the roadway laid (after that in Threadneedle Street) in Holborn, opposite Gray's Inn. It had been laid by Englishmen who were novices, and who followed slavishly the specification prescribed by the French engineers. That specification prescribed a layer of about 9 inches of lime concrete with inch of lime mortar. When the concrete was ready to receive the asphalt, a fire broke out in Holborn, and the barriers protecting the concretc were broken down; the place was flooded with water, the engines drove over the concrete, and the population of Gray's Inn Lane trampled it down. It was subsequently made good; the asphalt was spread, and some time afterwards the Val de Travers Company succeeded by inheritance, to its maintenance, and certainly it had been a "heritage of woe." For five or six years they had kept up the road at considerable expense and trouble, and at the end of that time they received the permission of the road authorities to relay the whole in two longitudinal strips, so as not to stop the traffic. On removing the asphalt it was found that the lime concrete had never set, that the mortar floating had never adhered to the concrete, but was mostly in powder, produced either by the action of the rammers, or by the traffic afterwards. They broke up the concrete, sifted out the lime, relaid the foundation with Portland cement, and put fresh asphalt on the top. That was done about four years ago, and the work had since proved satisfactory. Some of the workmen now in his employ, who had been previously engaged in Paris, had told him, that in several of the roads there the asphalt had been laid upon the existing macadam. The author

the material of a less thickness than 3 inch. Some years ago they laid -inch mastic footpaths, but the result had not been such as to encourage that mode of construction. It had even been adopted in some of the streets in the City of London having the heaviest traffic, such as Gracechurch Street and King William Street; but in four or five years the footpaths had become so much worn that it was thought desirable to take up the 21 inch mastic and lay down inch compressed, which had stood fairly well. He had been surprised to hear that his company had been credited with a preference for lime concretes over cement concretes for footpaths. That was far from being the case. The footpath referred to was laid as a sample under some special conditions. It was a fact, that in certain footpaths, particularly those in the suburbs, where there was little traffic, transverse hair cracks appeared from time to time. The first cracks to which his attention had been directed, were in the footway round the garden in Leicester Square, and appeared six years ago. The cracks were there to the present time; they had not in any way affected the stability of the work, but they were unsightly, and he should be glad to be able to prevent them. He had noticed that the better the concrete on which the footpaths were laid, the greater the number of cracks appearing in them, and the worse the concrete the fewer the cracks; indeed, if they laid the concrete bad enough there were no cracks at all. He had found it impossible to lay a horizontal riband of good cement concrete 3 inches thick without finding a hair crack at every 10 or 20 feet. The crack in compressed asphalt followed the crack in the concrete. Of course the footpaths were not subject to that hardening effect which was produced by the

rolling of wheels on roadways. He never nervous temperament. Nor was it enough remembered seeing a crack in an asphalt to pay attention to the durability of the roadway, although he had little doubt road; they had also to take into account that cracks might be found in the con- the foot-hold given to horses, and the crete underneath. Mastic asphalt being amount of tractive effort required, not more elastic than compressed asphalt, the only to draw the vehicles along the road, tracks were not SO numerous in it. but to start them; and they had further Nevertheless he was of opinion that, to consider the cost of construction, cæteris paribus, a compressed footpath maintenance, and cleansing. In regard was a more desirable one than a mastic to cleanliness, a good asphalt road was footpath. It was pleasanter to walk undoubtedly the best that could be conupon, owing to the absence of grit; it structed, and as to its impermeability to was handsomer, and it was also cheaper water, thus affording a protection to the to lay; moreover, it had not the disa- foundation, it was also an excellent mategreeableness of mastic footpaths, arising rial; but for slipperiness and deficient from the smell of the burning asphalt in foot-hold it was about the worst road in the cauldron. With regard to the sur- existence. As laid by the Val de Travers face duration, he believed that the compressed asphalt was better than the mastic. He was not surprised that very little had been said on the subject of slipperiness in connection with asphalt. The matter really lay in a nutshell. Roads when dirty were slippery, whether paved with granite or asphalt; but in the case of granite, a slipping horse might be pulled up by the joint of the second or third stone, whereas on an asphalt road there were no joints to prevent a fall. The true remedy was to keep the roads clean, as was done in Paris, where the asphalt road was a favorite one with cabmen and omnibus drivers. He was glad to find that, quite recently, the City authorities had arranged to have a certain number of hydrants used for washing the streets. He hoped that the experiment would be carried out carefully, and that the streets would be washed every morning before the traffic commenced.

Company, it was exceedingly durable, but it was costly in the first instance as compared with other materials. Taking all the requirements into consideration, he had arrived at the conclusion that for the surface of a road no material was equal to wood. But in order to obtain a good foothold on wood, it was necessary to leave spaces between the courses, principally for the want of which the old wood roads of twenty years ago had fallen into disuse. Other reasons for their discontinuance were that they had not been placed upon a proper foundation, and the blocks were not properly cemented or keyed together. He believed that the proper mode of using asphalt was to lay a damp-proof course of that material (to prevent the infiltration of water) on a foundation of concrete, and then to place wooden blocks upon the asphalt layer to take the surface wear of the traffic. The blocks were not only keyed to the concrete, but Mr. H. S. COPLAND said that the paper, they were keyed to each other by the although its title was "On the use of asphalt running into the joints, thus Asphalt in Engineering," dealt only with forming a monolithic slab of material, one kind of asphalt, the Val de Travers, which afforded a good foothold, could and of its use chiefly in the construction be readily kept clean, and was comparaof roads, or rather in the coating of road tively noiseless. As such a slab extended surfaces, which was only a small branch from one side of the road to the other, of a large and important subject. He the weight of the traffic was transmitted maintained that asphalt was wrongly over a large area, and was not confined used if employed as the surface of a to one block; the road being elastic, roadway. Engineers had to consider would wear uniformly; it would not other things besides the cleanliness of press too directly upon the concrete the material and its noiselessness. As to foundation, and particularly on one part the latter, though asphalt was free from of it, and a smaller depth of concrete one class of noise, it was attended with another-the clatter of the horses' hoofs, which was very irritating to persons of Vol. XXIV.-No. 1—4.

would suffice. Such a surface, if the wood were properly selected, would remain perfect for a number of years. In

16

Mr. E. A. COWPER observed that no one had touched upon the cheap method of making footpaths in the neighborhood of London, with tar and gravel, as now practised. A few years ago the material was mixed with stones and gravel, forming a sort of pudding, the whole thickness being put in at once, and as soon as the hot weather came, the tar exuded from the top, making a very bad, soft footpath. Of late years large stones alone had been put at the bottom, which, having received a coating of tar or pitch, just touched each other at points with their tarry surfaces. Above that a thin coating of finer material was placed, with a thin coat of fine stuff on the top. This made a splendid path; no tar exuded from the top, as any surplus drained down to the bottom, and the path was firm, hard, durable and clean.

Boulogne, four and a half years ago, he ted at a great speed, and were pulled up had laid down blocks only half the depth with difficulty. The durability of all of those used in London, for a traffic ex- roads depended to a great extent upon ceeding 120,000 tons per annum in a the character of the concrete. He found street 20 feet wide. The surface was that lias lime, properly used, was as good still perfect, and there were no depres- as cement, but it was necessary that it sions. The wear was solely from surface should be ground to a fine powder, and attrition, and had amounted to about that it should be fresh and uniformly inch per annum. The London company mixed, care being taken not to use too formed to work his English patent had much water. laid 60,000 square yards in London roads which had not in some cases worn quite so well as the road in Boulogne, in consequence of the wood not having been so well selected. The cost of such a road, fit for the heaviest traffic in Paris, would be from 12 to 15 francs per square meter (the amount given for the road described by the author being 17 francs), and the average cost of maintenance would not exceed 1s. per square meter per annum. He therefore maintained that his road, while offering all the advantages of freedom from noise, and being a better road for traction, would cost the municipality of Paris less, over a term of years, than asphalt. With regard to slipperyness, it appeared from the report presented by Mr. Haywood to the City Commissioners of Sewers in 1873, that on granite pitching one horse fell for every 132 miles traveled. On Val de Travers asphalt one Mr. J. LOVEGROVE desired, having had horse fell for every 191 miles traveled; some experience in the use of asphalt on and on wood pavement (not asphaltic public footways, to make a few remarks. wood pavement, but the nearest approach In the year 1869, when in Paris, he obto it), one horse fell for every 446 miles traveled. But the nature of the falls ought to be taken into consideration. Of the total number of falls on wood pavement, only one-eighth might be called dangerons, while three-sevenths of those on asphalt were dangerous. The danger was not simply from broken knees and from directly observable damage done to the horse, but from sprains in the attempt to regain a foothold. Injury of that kind was far more serious, more insidious, and less easy of cure. He concluded that, in all crowded streets, asphalt as a surface pavement should be given up. He agreed with Mr. Scott, that it might be used with advantage for the paving of narrow courts, alleys, and play-grounds for children; but the safety of grown-up people ought also to be considered, who, in crossing crowded thoroughfares, were constantly run over by horses, which on asphalt roads trot

served the peculiar condition of the roadway opposite the Tuileries; the asphalt appeared to have worked up into leaf-like layers, in a plastic state, and those layers occurred at distances of about 100 feet. He had little doubt that the cause was that the road had been repaired with asphalt too rich in bitumen. In the same year he also observed the paving of the road along the Rue St. Honoré; the process appeared to be different from that which was now adopted. There was first a layer, 4 inches thick, of hydraulic lime concrete, and then a layer of about 1 inch of mortar troweled. The concrete was beaten with instruments similar to the tools used by gardeners for beating turf. On the top was a 3-inch layer of powdered asphalt; the channels were pressed into form by a rammer about 9 inches long and 2 inches thick, and were well rammed; then a heated roller was applied over the whole surface. A roller with

much fall the traffic would be almost sure to keep to the fence line. It had been said that the quality of the Val de Travers asphalt was proved by its wearing to a film, but that was not peculiar to that asphalt, as the Limmer Company's asphalt behaved in precisely the same way. Common asphalt was more easily fractured, and would not wear to a fine film.

eight or ten carriage wheels, working of 3 inches of concrete. The work had upon a common axle, was also passed been executed partly by the Limmer over it in various ways for a considerable Company, the French Company, and time. Before he left Paris a considerable Leopold Stiebel. Where the paths were portion of the asphalt had to be taken narrow and the stream of traffic persistup, and he believed the whole was rein- ent in one track, the concrete was makstated He well remembered the care ing its appearance in small patches. with which the concrete used in Thread- Sometimes in wide paths the stream of needle Street was mixed, and the quiet, traffic was persistent next the fence line, steady way in which the foreigners and in these cases the path was apt to worked upon the asphalt. It was a unique wear out. He would suggest that it piece of work, and he would urge upon would be advisable in such instances to all asphalt representatives to endeavor lay an extra thickness. Of course, the to repeat it elsewhere. Great difficulty fall would influence the traffic; if too had been experienced in keeping in order a short piece of asphalt roadway opposite Hackney Town Hall, divided into three slips by tram lines, the tram-rail and the asphalt being too unlike to be kept together. He had recently tried a rough course of granite pitching at the side of the rails, which seemed to promise well. If well-dressed stones were laid in bond course, he thought they would Mr. ALFRED DAVIS observed that the answer very well. In 1872 a sample of compressed asphalt blocks used in Paris asphalt had been laid along the footpath were stated to have been unsuccessful. at Dalston Junction for a length of 550 In the United States a block was made feet, by the Val de Travers Company, of refined and tempered Trinidad asphalt and a second length was laid by the Lim- and finely crushed limestone, thoroughly mer Company. The first sample near heated and mixed in about equal proporDalston Junction, being subjected to the tions, and afterwards subjected to a unigreater wear, was renewed eighteen form pressure of 1 ton to the square inch, months ago; the other length was now or about 50 tons to the block. wearing near the fence line, the concrete standard size was 12 inches long, by 4 being exposed in patches. In 1874, a inches wide, by 5 inches deep. The layer of inch of compressed asphalt blocks had been laid in several of the was put along the busy part of Kings- New England States, and he believed land, and a path was also laid in a quiet were being extensively used in New street in Stoke Newington. Shortly after York, Philadelphia, and other American cracks appeared at intervals of about cities. He had seen a piece of this roadevery 12 feet, which he attributed to the way in Philadelphia, after six years' contraction of the material during cool- wear, and it appeared in first rate condiing. He did not believe that the con- tion, although the blocks were inferior crete was affected. He had that day to those now produced. In laying gone over a portion of the work and the compressed asphalt block road, a tested one of the cracks, and found the concrete foundation at least 4 inches concrete quite sound. He had placed upon the table rubbings of three wornout places; they looked more like a representation of the craters of the moon than a worn-out asphalt path, but it was an interesting mode of showing the condition of the footpath. Since 1876 about 160,000 superficial yards of gritted mastic asphalt had been laid in Hackney; it was inch thick, and rested upon a bed

The

thick was provided, over which a thin coating of gravel was spread; upon this bed the blocks were set close together and heavily rammed. The great advantage of this roadway was that it afforded a good foothold for horses, and at the same time possessed all the other advantages of asphalt roads as constructed in this country. The press employed in the manufacture of these blocks had a steam with a pressure of 90 lbs. per square inch. cylinder of 40 inches in diameter, worked

There was an ingenious automatic arrangement for forcing the block out of the mould, and carrying it away to any desired spot for storage.

not dried, and it was in that peculiar state that, although quite clean, it was very slippery. Grit had to be thrown upon it in order to enable the horses to Mr. FREDERICK Cox, Chairman of the stand, and that state of things continued Streets Committee of the City of London, until the afternoon, when the rain came said he had no connection with asphalt on and converted the grit into mud, companies or wood paving companies; which was probably so still, unless the he was not an engineer, and he had no heavy rain that had since fallen had scientific knowledge whatever, but per- washed it into the gullies. If cleanliness haps he might be permitted to make a could be accomplished, in his opinion few remarks as to the use of asphalt, asphalt would be the best roadway for past, present and future, in the City of all the main streets; its use had, however, London. The administrators of the City been attended with great difficulties, and Commissioners of Sewers gave encour- the authorities had not yet decided which agement to every projector to send in any plan to adopt. To show the difficulties kind of asphalt or wood pavement that that were experienced, he might mention was likely to be permanently useful. that three years ago the Commissioners About thirty different kinds had received commenced washing the streets, but they a fair and proper trial; most of them were threatened with an injunction from crumbled into dust or proved to be ut- the Court of Chancery for washing conterly worthless, but there were a few crete down the sewers. The Metropolitan that had stood a severe test. In his Board of Works, who had the care of the opinion the Val de Travers was the fav- main sewers, said, " It is all very well to orite company; but other companies had wash your grit into our main sewers, but laid down asphalt with good results. we must be careful what we do, because Mr. Haywood, the engineer of the Com- the Conservancy Board are threatening missioners, who probably had had more an injunction against us for raising shoals experience in roadways than any other in the bed of the river." That, however, person in the kingdom, reported, five did not frighten the authorities in the years ago, that, after trying the various City, who went to an expense of £10,000 kinds submitted, he found that good in providing large catch-pits to the gullies compressed asphalt was the cheapest, in the City in order that the deposits might dryest, cleanest, and most agreeable for be removed, which was done almost the general purposes of traffic, and Mr. daily. Then arose a question about the Cox ventured to say that if Mr. Haywood water carts, which caused so much obwere giving his opinion now, it would be struction in the crowded streets that the expressed in still stronger language. police interfered. The authorities had The Commissioners had carried out large endeavored to deal with that, and they paving works both with asphalt and had spent £20,000 during the last two wood, and probably the main reason that years in erecting hydrants in every street guided them in putting down so much and court in the City, both for the purwood was that the asphalt, especially pose of extinguishing fire and of watering when put down in great lengths, was the streets. Those hydrants were just found to be extremely slippery. In very completed, but had not been set to work. dry or very wet weather the foothold of With regard to wood pavement, he bethe horses was good, but when the pave- lieved it was one of the dirtiest and ment was muddy it was extremely incon- greasiest pavements ever put down in venient. It had been suggested that all the City of London. Dirt was carried that was necessary was to clean the from it over 100 or 200 yards of the streets, but what could be done with a asphalt, and rendered that which was place like Cheapside, when ten or twelve previously clean excessively dirty. He thousand vehicles passed over it every believed if the Commissioners could s day? After eight o'clock in the morn- ceed in getting clean asphalt, so as to ing it was useless to attempt to do any- avoid slipperiness, slipperiness, wood pavement thing of the kind. At six o'clock that would make very little progress in the very morning Cheapside had been thor- City of London, exept up gradients that oughly cleansed; at nine o'clock it had were not suitable for asphalt.

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