16 Mr. W. H. DELANO, in reply, said his as shown by the specimen of asphaltic experience in reference to scavenging concrete on the table. There were few was confined to Paris, where the work compressed footpaths in Paris. In 1874 was effectually done both in wet and dry he laid on the Pont Royal about 200 weather. Gangers were constantly at square meters of this material, under the work, and they were paid about 3d an orders of M. Allard, now Chief Engineer hour. The gully holes placed under the of the City of Paris, and it was now in curbs were large and the drains were good order. At one part it was laid roomy, so that the slush was easily inch thick, in other parts inch, and in passed down them. Hydrants had been others 1 inch. It had a better appearerected all over the city, and after heavy ance than mastic, but it cost more, berains they were used to flush the road- cause the thickness was greater. The speways and carry the mud into the drains. cific gravity of compressed and mastic asOf course it got into the river and phalt was about the same, but the grit put formed banks, but that was the affair of into the mastic made it harder than the other authorities. He would suggest compressed material. The statement that that the catchpits to which Mr. Cox had asphalt neither contracted nor expanded alluded might be emptied by a pneu- was certainly an error. Of course the matic system of pumping into carts. For- laying down of footpaths with gritted merly mud carts were employed with re- mastic depended a great deal upon the clivolving brushes to take up the slush; but mate. In Marseilles the workmen would he believed they had been superseded. put into the cauldrons as much grit as they It was evident that scavenging could not did asphalt, making a stiff mixture, which be done in London without considerable required great muscular strength to lay expense; but probably London mud, like down inch in thickness, but when it Paris mud, contained fertilizing qualities, was laid it answered very well. No pracso that some set off might be obtained. tical worker of asphalt would ever use With regard to the granite sets in Paris compressed asphalt as a coating for to which Mr. Ellice-Clark had referred, masonry, because it had not sufficient he had given particulars of the cost, and elasticity. Coatings of masonry were also of the cost and maintenance of the generally put down inch thick, and macadam, in the appendix to his paper, they required a good deal of bitumen; and an interesting report had been pre sometimes the layers were vertical, at sented upon the subject by M. Vauthier. other times convex, and frequently had As to the cracks which had been so fre- to be inserted in recesses in the mansonry quently mentioned, he believed they re- prepared for the purpose. Portland sulted in nine cases out of ten from the slabs had been suggested as a concrete, concrete. If mastic asphalt was placed but he did not think they would answer, on wet concrete it would blister and because they would require concrete unsometimes crack, especially if the bitu- derneath to keep them level. He had men used as a flux to melt it was not been reproached for not having alluded well purified. Some engineers used to asphalt as a covering for roofs, but straight joints to prevent cracks. He his experience having been limited to had also seen hoop iron put in between France, where such applications were the concrete at certain distances when it well known, particularly in the south, he was not too thick. It was always well supposed that engineers in London who that the asphalt, liquid and mastic as were familiar with such applications well as compressed, should be sufficiently would themselves refer to them. The thick. Unfortunately Municipal Boards applications of asphalt were almost often required things to be done cheaply, endless. He had just seen a veteran and hence the thickness of the asphalt asphalter in London who had shown him was less than it ought to be. In Paris, some work that he had done at the Horse where a fifteenth part had to be renewed Guards stables forty years ago. Up to every year, thickness was not such a the 31st of December, 1877, the chief desideratum. In the case of gritted mastic, the thinner the mastic the finer the grit should be. Where the mastic was thick, a coarse grit might be used, cause of the want of stability of the compressed asphalt roadways in Paris. was owing to the hydraulic lime concrete being only 4 inches thick, covered with a lime mortar floating, whereas a layer of test would class it as a material for road6 to 9 inches of Portland cement with- ways. It was quite possible to make out floating was indispensable. Since bad work with good materials, though the 1st of January, 1878, Lobsann as- the converse was not true. Still, when phalt had been used instead of Val de good asphalt, properly ground and Travers and Seyssel, as heretofore, which, heated and well laid by careful workaccording to the report of the Paris en- men, did not stand, it was almost always gineers, had not sufficient stability. Seys- the fault of the concrete. Laying on sel mastic was chiefly employed in wet concrete, or using burnt powder was France for footpaths and coatings for sometimes a cause of failure. Sets of masonry, whereas Val de Travers had pure Seyssel and Val de Travers powder, been more largely used for compressed compressed in a mould 4 inches square asphalt roadways, although by no means and 2 inches deep, had been successfully exclusively. Wood pavement had not used in Paris, but there would be a diffisucceeded in Paris, the only important culty in repairs; it was also cheaper to specimen on the patent plank foundation lay hot powder in large towns. Some being the Rue St. George's, which was artificial sets, 8 inches cube, composed, partially in a bad state, although subject he believed, of gas tar mastic and only to light traffic. In several cases gravel, had been laid last autumn in wood pavements had been taken up in the Rue Neuve des Petits-Champs, at Paris within the last eight years, and the angle of the Rue Vivienne. The replaced with granite sets and com- piece had been frequently repaired, as pressed asphalt. Wood was not a the surface wore away and crumbled unmaterial of invariable density like com- der the traffic, which was not heavy. pressed asphalt, the heart being al- He had no confidence in bituminous conways harder and less absorbent than crete for roadways, except when used as the outer rings. It had, however, the a foundation for compressed asphalt, ingreat advantage of comparative insonor- stead of Portland cement concrete. With ity, though vibration was perceptible, reference to the Seyssel and Val de Traand it was excellent for inclines exceed- vers mines, he had hoped that the engi ing 1 in 50. He thought that sound neers who had worked them would have oaken sets, with beveled edges carefully been present and given personal explanalaid on good cement concrete, with inch tions. He might mention that the mines joints filled in with pure asphalt mastic, were easily worked; there was no chokewould render good service for roadways damp in them, and little water. The in dry climates, but he doubted if any rock was blasted with powder, dynamite pure wood pavements would last in Paris not being used because the asphalt was or in London much over three years tenacious in its nature. It had been without costly repairs. The smell from stated that the test of asphalt was its rotting wood pavements saturated with durability. His object in writing the the filth of large towns must be deleteri- paper was that any engineer, surous. It was well known in Paris that veyor, or architect, in specifying Sicilian asphalt had been taken out of asphalt might have some other test. the list of asphalts approved by the city Asphalt might be adulterated; but the engineers for roadways since 1872. He had been prohibited from employing about 1,500 tons from Ragusa, Sicily, for roads in Paris, and had used a good deal of it as ashlar. This rock was available for flags, staircases and balconies; it was susceptible of delicate carving for architectural ornaments. There were three qualities, one rich in bitumen, the second medium, and the third poor, the latter being a coarse-grained yellow stone with the appearance of sandstone. If it would last three years under heavy traffic in London without repairs, such a tests he had given would enable an architect or engineer to satisfy himself. With reference to the question of nomenclature, "asphalt concrete" had been alluded to in Mr. Deacon's paper; but he was sure from the context that gas-tar concrete was meant, which was a different thing. Mr. Cowper also had referred to pitch and tar pavements; but pitch and tar were not asphalt. It was most important not to confound them in specifications, as their respective values and properties were widely different. Considerable areas of compressed asphalt had been laid in Berlin, Vienna, Pesth, Brussels, and New York, and he regretted that no engineer had described the mode of laying. CORRESPONDENCE. periments with the material, but as far as they had gone they were well satisfied. Mr. MAURICE BIXIO, President of the Paris General Cab Company, owning about twelve thousand horses and six thousand vehicles, gave the results of his experience as to the most suitable material for roadways for vehicular traffic. The worst pavement was porphyry (grey Belgian granite sets, 4 inches by six inches). Falls of horses were much less uniformity the longer would be the endurfrequent on asphalt, macadam, or rough pitching (sets of Fontainebleau gritstone 8 inches cube). For the horses, falls on asphalt were less dangerous than on any other material. Beyond all doubt traction was less on asphalt than on any other pavement. His company had made many experiments on this subject, from which he would quote, at random, the following, relating to the French four wheeled cab, weighing 658 kilogrammes (1,447 lbs.): Traction on rough pitching..... Traction on small sets...... Traction on mac Kilogrammes. 16.37 (36 lbs.) 14.79 (32.5 lbs.) Min. Max. Mr. ERNEST CHABRIER wished to deprecate a practice which had been tolerated for some time in the depots of the City of Paris, viz., the mixture of several kinds of asphalt, with a view to obtain an average quality which would be supposed capable of meeting general requirements. The principal quality to be sought for in rock asphalt for laying on roads was, the greatest possible homoand equal regularity in the amount of geneity in the grain of the limestone, the bituminous matrix. The greater this ance of the asphalt roadway. He would illustrate this by referring to the fact, with roadmaking, that a mixture of hard well known by all engineers concerned surface than one of the softer material with soft metal formed a less enduring alone. The uniform wear of all parts maintained cohesion, which, on the contrary, was rapidly destroyed when a piece of hard stone was, from continual vibration, displaced, without being crushed, thereby leaving a hole. When asphalt rock was not suitable for road surfaces it was either too poor or too rich. In the first case the particles did not cohere; in the second the carriage wheels sunk into the material. The practice had been allowed of mixing these two kinds of rock adam....... 14.0 to 20.5 (30.8 to 45 lbs.) in proportions impossible to be accurate Traction on com pressed asphalt (Val de Travers) 12.79 (28 lbs.) It ly determined, the process being left to It was probable, though difficult to establish otherwise than by comparison, that the wear and tear of the different parts of a vehicle was less rapid on asphalt than on other pavements. But the comparison did not apply in its entirety to macadam, in which case the tires of the wheel and the horse shoes were the only parts that wore out more rapidly than on asphalt. The difference of wear was due to the jolting produced by sets, which naturally induced friction between Mr. LAVALLARD, Director of the Stock all parts susceptible to that action. He and Forage Department of the Paris thought that traction being less, fatigue General Omnibus Company, gave some to the horse would also be less; but that information relative to the traction of was only an opinion, and not based on heavy vehicles on asphalt carriageways. actual experiment. Asphalt was excel- The standard omnibus of the Paris Comlent also for granaries and for lining pany weighed from 1.67 to 1.77 ton empwooden mangers. For the paving of ty, and from 3 to 3.6 tons when full. The stables his company had made few ex-diameter of the fore-wheels was 4 feet, of the hind-wheels 5 feet, the width of shocks were imperceptible. Although, the tires being 24 inches. The new three- under the conditions named, horses fell horse omnibus weighed, when full, from more frequently on asphalt than on gran 5 to 5 tons; the diameter of the fore- ite sets, the injuries received were less wheels was 3 feet, and of the hind serious. It, however, resolved itself into wheels 5 feet, the width of tires be- a question of shoes, and he thought the ing 3 to 3 inches. The company's adoption of the Charlier horse shoe had tramway omnibus* weighed, when full, met the difficulty. His company had 6 tons, and the diameter of the wheels found that asphalt succeeded perfectwas 3 feet throughout. The result of ly as a flooring for granaries and fordaily experience showed that when the age stores, but not so well for stables, weather was not very warm and the as- where it had in most cases to be abanphalt remained hard, traction on this doned, owing to the weight of the horses material was less than on ordinary road- (from 10 to 12 cwt. each) causing depresways; but that when the asphalt became sions in the material when softened by softened, by the heat of a fierce sun, the warmth of the recumbent animal. traction became considerable and aug- The urine collected in these holes, and, mented with the rise of the thermometer moreover, the asphalt was too smooth for and the weight of the vehicle. When the the straw, which was always found kicked asphalt was either dry or wet it afforded out behind the stall. Perhaps for horses a good foothold for the horses. But of a lighter build the inconvenience when the asphalt was beginning to get wet or beginning to dry the horses had much difficulty in keeping up. Under such conditions the asphalt was slippery, and the fall of the horses became frequent. This did not, however, affect the traction of the vehicles, which still remained less than on other roadways. The wear and tear of tires, axles, harness, &c., was less on asphalt because would not be so great. Latterly they had had reason to believe that the consistence of the subsoil had some influence on the question, because they had stables wherein asphalt floors laid ten or twelve years ago were still in good condition. The cost of maintaining the asphalt laid along their tramways was 1 franc 20 centimes per square metre per annum. PROPOSED SYSTEM OF By ED. M. ROGERS. Contributed to VAN NOSTRAND'S ENGINEERING MAGAZINE. AT present the railroad system of the serious objections which have heretofore world has reached an extent of 123,000 prevented their general introduction. miles, involving in its construction an With very few exceptions the overcomexpense of $11,255,000 and the con- ing of steep gradients is confined to the sumption of more than one-half the friction of smooth drivers on smooth total iron production. This excessive rails. cost is due, in a great measure, to the At a very early date in the history of necessity of using comparatively light railroads, the discovery of coal in the grades rather than making the roads Lackawanna Valley directed the attention conform to the surface of the ground. of engineers to the problem of its transWith a view of obviating this difficulty many ingenious systems of gravity railroads have been proposed, with varying success, but they are all open to *The vehicle used on the tramways of the Paris Omnibus Company is not a car as usually understood, but merely a big omnibus on flanged wheels. The tramway companies use cars of the same character as those in London. portation, across the mountains, to a seaboard market. The result of their investigations was the construction of the noted gravity system of the Delaware & Hudson Canal Co. This system involves two independent sets of inclined planes, each set being arranged in the order of a short, but steep plane, followed by a long one, the inclination of which is were to be thrown in at such places as reversed and is only sufficient to over- the character of the country might warcome the friction of the cars. At the rant. A plane of one in six is the maxisummit of these planes are situated sta- mum inclination over which a locomotive tionary engines, provided with suitable can proceed, without a load, and in all drums and endless wire ropes. Arriving kinds of weather. Since, then, none of at the foot of a steep incline, the trains the planes were to exceed this limit, the are attached to the rope and elevated to locomotives could always climb them, the summit by the action of the engines, and it only remained to provide suitable being then in position to descend the means of elevating the trains. To aclong inclines in virtue of their potential complish this, each locomotive was to be energy. provided with winding gear and steel wire rope, driven by auxiliary engines. In addition to this they were to carry powerful gripping struts which, by their action on the rails, might be capable of holding the entire train. Arriving at the foot of a plane the engine was to be uncoupled and proceed up the hill, at the same time playing out the wire rope from its winding drum. At the summit it was to be anchored by means of the gripping struts, thus virtually changing the entire machine into a stationary winding engine, by the action of which the train might be elevated. The second set, which is in some places several miles distant from the first, has its planes reversed and is intended for the return of the empty cars. This is, doubtless, the cheapest method of transportation, through mountainous districts, provided there is traffic enough over the line to keep the stationary engines in constant use; for what would represent the friction of a train for a long distance on a supporting grade is concentrated in overcoming the gravity of a short plane. Yet, notwithstanding the utility of this method, in special, and the entire railroad system, in general, there is still a want felt which calls for, and has, in some measure, received the attention of engineers of to-day. I speak of lateral roads through mountainous districts intended as feeders of main trunk lines, over which the traffic is not sufficient to warrant the expense attending the construction of long lines, with light grades, or the operation of gravity roads with stationary engines and rope haulage. Since it is the purpose of this paper to propose and discuss a system of planes for lateral roads, perhaps it will be well to mention some of the kindred devices already in operation, in order to bring them into comparison with the proposed plan. In June, 1876, an article appeared in this MAGAZINE by Mr. Henry Handyside, stating the problem of inclined roads, and proposing to solve it in the following manner: The greater portion of the line was to be constructed with such a grade that the ordinary locomotive might be able to draw over it trains sufficiently large to accommodate the traffic of the region through which it passed. But, in order to overcome the required elevation, occasional planes, not exceeding one in six, This method was practically tested in England, and met with some success, though its introduction was very limited, and, I believe, it has since been abandoned. Another method which has received some attention, but which has not, as yet, been practically tested, is briefly as follows: The grade of the road is arranged like that of Mr. Handyside; that is to say, there are no inclines so steep but that a locomotive, detached from its train, can climb them. The method of operation is also similar to that above described, the only essential difference being in the manner of changing the locomotive into a winding engine. In this case, upon arriving at the summit of a plane the locomotive is anchored over a pair of friction drums on which the drivers act, causing them to rotate and put in motion a set of winding gear, by the action of which the train is elevated. The main advantage which this system offers over that of Mr. Handyside is, perhaps, the difference in expense between the equipment of the planes with suitable drums and gear in the one case, and providing each locomotive with the necessary appliances, in the other case. This would, of course, vary |