1; *K^ rf€^^!:J^^ € m^ B The Barber Asphalt Paving Co. IS THE Oldes It has, up to Jai seven Cit lei No Asphalt Pa ever , This compan} with Trinidad ^ Wood, Stone, French Glass T ^ /45 look >33o presi-:nti-:i) by •mpany ents in Twenty- treets, of a a of United States has lement. id replaced them ; extent : sq. yds. LOAL Tak AiNJJ VULCANITE, 04,^^19 Macadam. - - - 415,686 Total. A. L. Barber, President. F. V. Greene, 1,417,514 D. O. WiCKHAM, Treasurer. E. B. Warren J Vice-Presidents. J. C. Rock, Secretary, GENERAL OFFICES I Le Droit Building, cor. 8th and F Sts., Washington, D. C. Washington Building, i Broadway, New York City. .'1 BrennanRockCrusher ROAD ROLLERS, CONVEYORS, ROCK DRILLS. The -STANDARD^' Machine rOE OEUSHING STONE, POK MAKING MACADAM ROADS. THE ONLY ROCK CRUSHER WHICH PROPERLY Cubes and Siz^es Stone. 40 Per Cent. Less Power Used Crushed. per Ton of Stone ' 5 X 20 crushes 8 to 12 tons, 10 H.P. Capacities per tons. 7 X 20 '' hour, , 8 X 25 " 10 X 25 " 12 to 15 " 15 " 15 to 20 '' 20 " 20 to 30 '< 30 '' 12 X 37 ^ 16 X 48 *' 30 to 40 " 40 *' 70 to 100 *' 80 " GENERAL AGENTS, PIERCE & THOMAS, 42 Cortlandt Street, New York. P NGINEERING N EWS AND AMERICAN RAILWAY JOURNAL. PUBLISHED WEEKLY BY Encineerinc News Publishing Co., Tribune Building, New York. Sixty Pxges. Subscription Price- If^ ''^" Annum. SUBSCRIPTION PRICE. -^^2 FOR FoUR MONTHS. ENGINEERING NEWS contains each week twenty- four pages of valuable read- ing matter, covering the entire field of engi- neering science in both this and foreign coun- tries. Railways, highways, water-works, manu- facturing and technical, contracting and mechanical and electrical industries are fully reported, and detailed working drawings and full descriptions are given of all the more important and noteworthy structures and enterprises. Record is kept of the proceedings of all the engineering and technical societies and clubs, and the latest technical books and magazines are fully reviewed and discussed. The correspondence columns contain com- munications from engineers, contractors and others regarding matters of current interest. These are only a few of the many features of interest and value. On all technical questions relating to railway and water-works construction and administra- tion, Engineering News is an acknowledged authority. THE SCIENCE OF ROAD MAKING. CLEMENS HERSCHEL, M. Am. Soc. C. E. CONSTRUCTION - MAINTENANCE OF ROADS. EDWARD P. NORTH, M. Am. Soc. C. E. NEW YORK: ENGINEERING NEWS PUBLISHING COMPANY, 1890. TC 4S" PREFACE The science of roadmaking was revised by Mr. Clemens Herschel in 1877, and the paper of Mr. Edward P. North was presented to the American Society of Civil Engineers in 1879. To the one was awarded the First Prize of the State Board of Agriculture of Massachusetts, and to the other the Norman Gold Medal of the American Society of Civil Engi- neers. Though considerable advance in processes and machines has been made since these dates, these two papers still contain more con- densed and valuable information on- a subject now attracting wide-spread attention than any similar publication of which we have knowledge. Literature on the actual detail of road-making is scarce and fragmentary ; and it is with the hope that these two otherwise practically inaccessible papers may prove profitable reading to eingineers and others interested in road-making that they are now reprinted. Gfft Mrs.Galllard Hunt April 28, 1933 . i'"^ S' TABLE OF CONTENTS. PART I. Introduction. Laying Out a Road 6 Considerations which Determine Best Location 6 Roman vs. Modern Road Builders 6 Minimum Radii in Mountainous Districts & Concerning Grades, Telford's Rule 7 Experimental Conclusions 7 Nomenclature of Roads 7 Effects of Various Grades on Amount a Horse Can Pull 8 Width of Roads 9 Actual Field Work of Laying out the Road 10 Making the Road Bed 10 Earthworks, Data for Cost of 11 Transporting Earth : Shovels and Wheelbarrows 11 Loosening the Earth (Table) 12 Portable Railroad and Hand Cars 13 One-Horse Carts 14 Shrinkage of Different Soils 14 Drains and Culverts 15 Bridges 17 Making the Road Surface 17 Foot Paths 17 Riding Paths 18 A Good Road Surface 18 Value of Old Engineering Treatises on Roads 19 Experience of Older Countries 19 Chinese Roads 19 Macadam's Invention 19 Foundation, or Telford, Roads 20 Roadbuilding in Baden, Germany 20 Rules in Prussia for Inclinations , 21 Macadam Top 21 Material for Road Covering 22 Crushing Machinery 23 Spreading the Material 27 Practice in Bohemia 27 Road Rollers 27 Literature of Steam Road Rollers 28 Description of Best Horse Road Roller 29 Estimating Cost of Macadam Road 31 Gravel Top. Central Park Roads 33 Comparative Cost of Good and Bad Roads 35 TABLE OF CONTENTS. Keeping Roads in Repair 35 Value of Constant Repairs 37 Value of Annual Repairs 37 Tresaguet's Method in Baden 37 Comparative Tables of Cost 38 How to Repair Roads on the Continuous System 39 Repairs of Macadamized and Much Frequented Streets in Cities 41 Pavements and Trackways 42 Stone Pavements 42 Wooden Pavements 43 Cast Iron Pavements 44 Asphalte Pavements 44 Trackways and Plank Roads 44 On the Resistance to Motion in the Force Required to Move Vehicles on Different Kinds of Roads 45-49 PART II. Best Method of Superintending the Constructing and Repairing OF Public Roads 50-60 APPENDIX. An Act for the More Perfect Construction and Maintenance of the Common Roads on Highways throughout Massachu- setts 61-64 The Construction and Maintenance op Roads ; Earth Roads 65-67 Macadam 67-82 Stone Pavements 82-83 Wood Pavements 83-88 Asphalte and Bitumen 88 Compressed Asphalte 90 ' Asphaltic Mastic 95 Bitumen Mastic 97 Tar Mastic 99 Appendices 100 No. 1. Extract from Birmingham (England) Specification 100 No. 2. Extract from Specification for Telford, Macadam and Trap Block Gutters on Fifth avenue, N. Y 100 No. 3. The Gellerat Roller. \ 103 The Lindelof Roller 104 The Aveling & Porter Roller 104 The Ross Roller 106 No. 4. A Part of the Contract for the Construction and Maintenance of the Streets and Sidewalks of the City of Jassy 107 No. 5. Abstract of Specifications and Schedule of Prices for the Con- struction and Maintenance of Footpaths and Sidewalks in Asphaltic Mastic, and the Places and Roadways in Compressed Asphalte be- longing to the Municipal Service of Paris, from January 1, 1878, to December 31, 1882, Paul Crochet, Contractor 112-117 Discussion on the Construction and Maintenance of Roads 119 N[ote on the Nomenclature of Bitumen 143 THE SCIENCE OF EOAD MAKING. INTRODUCTION. This treatise was written in answer to the printed circular of a Committee of the Board of Agriculture, calling for "treatises upon the science of road making, and the best methods of superin- tending the construction and repair of public roads in this Com- monwealth." This circular was issued about the middle of December, and as the time for writing and sending in the called-for essays was limi- ted to January 28, the writer has thought it best, no specific char- acter being prescribed for the treatises, to attempt to write one suitable to be so called from the stand-point of the fublic^ rather than from that of the civil engineer, and, giving results rather than the methods of arriving at them, to be as concise as possible. The Science of Road Making. Starting, then, with the first of the two subjects mentioned in the circular, — the science of road making, we can divide this into three periods: i. Laying out a road ; 2. making the road-bed, which includes all earthworks, cutting and filling, culverts, drains, bridges, even tunnels, etc.; and 3. the making of the road surface; ♦A First Prize Treatise awarded to the Author by the State Board of AgricuL ture, of Massachusetts. THE SCIENCE OF ROAD MAKING. to which, not improperly might be added, 4. keeping the road in repair. Laying out a Road. The considerations which determine the best location of a road, are those arising from the nature of the travel it is proposed to accommodate; that is, from the admissible grades, radii of curves, etc. Given two points it is desired to connect, with no intermedi- ate point where the road is to touch, that route is the best which will cost least to build and maintain, the grades and curves being kept within bounds ; and to find this location constitutes the whole problem of the engineer. | In older countries, where trade and manufactures are more settled and unchanging than in the United States, the probable future travel upon a road about to be laid out and built, forms a material element in the data that govern its alignment and grades. A very able and clever article upon this subject may be found in the Journal of the Society of Civil Engineers and Architects at Han- over," for the year 1869, and also in pamphlet form. It is in the German language, written by Launhardt, Superintendent of High- ways (and a civil engineer) in the Hanoverian provinces. The Romans built all of their roads in perfectly straight lines, up hill and down, at a very great expense, as being absolutely the shortest distance between two points. At a later period in history, it was argued that a road must be winding to be agreeable, and many were so built only for this reason. The modern road- builder or engineer in general, ignores any such considerations, and has for his aim only to achieve the most, at the least present and future expense. ^ As regards curves in roads in a hilly or mountainous district, we have then the rules never to make a smaller radius than 30 feet, and that only in extraordinary cases. On roads where long log- ging or other wagons may be expected, the smallest radius ought to be 50 or 60 feet ; and, in general, 40-45 feet is none too much. A rule sometimes followed in constructing mountain roads, is, where the inclination is i or 2 in a hundred, f heavy teams require f In describing grades, the first figure gives the vertical height which is ascended in a horizontal distance given by the second figure. Both figures must of course be taken to refer to the same unit of length, thus : 100 feet in 120 feet, 100 inches in 120 inches, or 100 miles in 120 miles, all express the same inclination to a level plane, and are more general in their application than the ways of expressing grades in so many inches to the foot, or feet in one mile, etc., etc. THE SCIENCE OF ROAD MAKING, 40/ and light ones 30/ radius; with a grade of 2 or 3 in a hundred, heavy teams require 65/ and light ones 50/ ra- dius. Where a reverse curve [shaped like the letter S] occurs, there should be a straight piece connecting the two curves [Fig, I.] On the contrary, where the two curves to be connected are concave in the same direction, the ^®* *• connecting link should be curved also, and not straight, [Fig. 2.] On the length of the curves the grade should be made easier than on the parts of the road immediately ad- joining. As regards grades, to start with mountain paths, we find pedes- trians able to walk up an inclination of 100 in 120; mules, ponies, ■etc., 100 in 173. For roads, Telford's rule was, that for horses attached to ordinary vehicles to trot up a hill rising 3 in 100, was equal to walking up one of a 5 in a 100 grade. Experiments have shown that — 1. On a road falling 2 in a hundred, vehicles would run down of themselves. 2. On the same kind of road, but having an inclination of 4 in a hundred, light vehicles had to be held back lightly, loaded ones with considerable force. 3. On a road having a fall of 51^^ in a hundred, light vehicles had to be held back with considerable force, or if a brake was applied they had to be pulled, whereas heavy or loaded vehicles had to be braked to keep the horses from being speedily exhausted. On inclinations steeper than 5 in a hundred, the rainwater run- ning down the road is apt to do some damage to the road surface. The regulations of different countries having a long experience in road building, such as France, Prussia, Baden, etc., vary some- what, but the following is the general result: In treating of roads, it often renders the subject much clearer, to divide them into three classes : first, second, and third class roads, or, as we might also say, state, county and town roads. Accepting this nomenclature, we have this: for first-class or state roads, the 8 THE SCIENCE OF ROAD MAKING. greatest inclination should not exceed 3—5 in a hundred ; second-class or county roads, 5-7 in a hundred; third-class or town roads, 7-10 in a hundred. A road rising 10 in a hundred is not supposed ever to have any heavy teams upon it. In ascending a hill it is wrell and proper to decrease the grade as the top is reached, and in the same measure as the horses get tired. Thus, if a first-class road starts up hill with a grade of 4^ per hundred, it should gradually dimin- ish to 4 and 31^ in a hundred, and end near the top with a grade of 3 in a hundred. Launhardt, the superintendent of highways, and engineer, men- tioned in the previous note, has a valuable article on the subject of the best grades for highways, in the Engineering journal there mentioned, for the year 1867; re-printed also in pamphlet form- He shows in this article that, according to the received formula that expresses the relations between the tractive force, the velocity in feet per second, and the daily working hours that go to pro^ duce the maximum amount of work that can be got out of a draught-horse, a uniform grade between any two points, except perhaps in curves, and, if desired, for resting places, is the grade that tends to enable the horse or other draught animal to produce the most work per diem. If a grade of 4 or 5 in a hundred must needs be kept up for some distance, then it is well to have resting places 40 or 50 feet long, having a grade of only \% ox two in a hundred, in the line of the road at proper intervals. An expedient adopted by TeU ford, the eminent English engineer, in order to avoid making a. piece of road a mile long, on a less grade than 5 in a hundred, on account of the increased cost this would have occasioned, and yet not have this part of the road too much more tiresome for the horses than the rest, was to make the road-surface on this mile of a much better quality than on the remainder; the additional cost required for the improved road-bed amounting to only about one- half of what it would have cost to reduce the grade to say 4 in a hundred, as will be again referred to under the head of trackways.. In sharp curves the grade should be only i or 2 in a hundred or level. The following table gives the effects of various grades on the amount a horse can pull, and is based on calling the load a horse will pull on a level, one : — THE SCIENCE OF ROAD MAKING. Then, on a grade of 1 : 100, a horse can pull M «( i: 50, " «« «( I: 44. « «< « I: 40, ti «< •» I: 30, *• « 4< I: 26, '* 1* " i: 24, •• M «4 I: 20, " t< 14 I: 10, •• 0.90 0.81 0.75 0.72 " 0.64 0.54 0.50 0.40' 0.25 To determine whether it is most advisable to go over or around a hill, all other considerations being equal, w^e have this rule : Call the difference between the distance around on a level and that over the hill , t/, the distance around being taken as the greatest, and call h^ the height of the hill. Then in case of a first class road, we go round when d is less than \6 h. And in case of a second class road, we go around when d is less- than \o k. When the height of a necessary embankment gets to be more- than 60 or 65 feet, a bridge or viaduct will be found cheaper, and the same measure, 60 feet, applies in case of tunnels, they being" cheaper at that depth than open cuttings. Under the head of laying out roads, something should be said of their width. Speaking only of such roads as are not apt to turn- into streets from their proximity to towns and cities, it is well not to make them too broad, for the less the width, the less the cost of construction and maintenance, and a good 23 feet road is much bet- ter than a poor one 40 or more feet wide. Each rod (16^ feet) in width adds two acres per mile to the road. An agreeable form of road is to have on each, or on one side of the same, a strip 5 or 6 feet wide, sodded, and then a sidewalk equal in width to one-eighth the width of the roadway. The intervening strip above mentioned, is planted with trees and at intervals of 200-250 feet furnishes storage places, 30 or 40 long, for the materials used in the road repairs. The width of first, second and third class roadways may be given as 26, 181^ and 13 feet, with a tendency during the last ten years to have none, except in the vicinity of cities, wider than 24 feet, and the rest correspondingly narrower. In view of the changes constantly going on in this country in the value and settlement of lO THE SCIENCE OF ROAD MAKING. land, it would probably be well always to lay out a road 50 or 60 feet wide, but to build the road proper of the width above indi- cated. With all these rules and data in mind, the real work of actu- ally laying out the road on the ground and on a map is next in order, and this comes so entirely within the province of the civil engineer, and is a matter requiring so much explanation and study, that it cannot well be introduced within the limits of this treatise. It is in this part of the work that a little skill and labor well spent may be productive of very great saving in the cost of the whole work and it should not be left to the inexperienced or unskilful.* Making the Road-bed. Under this head are included, earthworks, drains, culverts, bridges, stay walls, etc., etc., all matters requiring a special kind of skill to construct properly. The writer believes it impracticable to write a book which shall at once be interesting to and therefore valued by the public, and of value to the professional man, and thinks an attempt so to do results always in a failure in both direc- tions. True to the determination expressed in the introduction, he proposes, therefore, to treat under this head mainly with those parts of the subject in which the public at large is most interested, for example, the data for the cost of earthworks, general information relating to drainage, bridges, etc. * Gillespie, in his treatise on "Roads and Railroads," gives two forcible instances of the amount those roads which might properly be called chance roads, can be improved by a road-maker of skill and understanding. An old road in Anglesea, England, rose and fell, between its two extremeties, twenty-four miles apart, a total perpendicular amount of 3,540 feet ; while a new road, laid out by Telford between the same points, rose and fell only 2,257 f^et ; so that 1,283 feet of perpendicular height is now done away with, which every horse passing over the road had previously been obliged to ascend and descend with its load. The new Toad is besides two miles shorter. The other case is that of a plank-road built in the State of New York, between the villages of Cazenovia and Chittenango. Both these villages are situated on Chittenango Creek, the former being eight hundred feet higher than the latter. The most level common road between these villages, rose, however, more than 1,200 feet in going from Chittenango, to Cazenovia, and rises more than four hundred feet in going from Cazenovia to Chittenango in spite of this latter place being eight hundred feet lower. That is, it rises four hun- dred feet where there should be a continual descent. The line of the plank- road laid out by George Geddes, civil engineer, ascends only the necessary eight hundred feet in one direction, and has no ascents in the other, with two or three trifling ■exceptions of a few feet in all, admitted in order to save expense. The scenes of similar possible improvements are scattered all over this and the rest of the States ; and these facts are still more or equally to be borne in mind in laying out new roads, where the ounce of prevention may take the place of the pound of cure. THE SCIENCE OF ROAD MAKING, II Earthworks. The basis of all values is the daily wages of a common unskilled laborer, and in the data given below, this figure, whatever it is from time to time and in various places, must be taken as unity, or the standard measure. The cost of earthworks may be divided into three parts — (i) cost of loosening the earth, (2) cost of transport, and (3) cost of forming the transported earth into the desired shape. The cost of the first part depends materially on the kind of earth to be handled. The cost of the second, mainly on the distance the earth is to be moved. We find by experience, that in digging and loading or throwing 5-10 feet horizontally with a shovel, we obtain for different mate- rials the results of the table on the next page. Transport of Earth. Throwing with a shovel, — This is to be done only from 5-12 feet in distance or from 5-6 feet vertically. To throw 5 fv^et verti- cally, costs as much as 12 feet horizontally, that is to say, if 30 feet horizontally cost per cubic yard, one day's wages divided by 8.4 the same distance vertically will cost about 21^ times as much, or more exactly, one day's wages divided by 3.5, whence is seen the economy of using windlasses, etc., instead of "stages,**! in shovel- ing earth vertically. The table gives the cost of shovelling earth certain distances, expressed in the number of cubic yards a laborer's day's wages will pay for. Distance of Throw in Feet. \ > Whether done at one operation, or by means of so- called "stages." Number of cu. yds. which can be trans - ported at the cost of one laborer's day's wages. Remarks. O-IO, . Horizontally, No " Stages." 23.5 10-20, . it I stage. 12.6 \ Wheelbarrow 1 cheaper. 20-30, . (( 2 stages. 8.4 0-5. . Vertically. No stages. 14. 1 5-10, . " I stage. 8.8 fBy a " stage" is meant the operation of one shoveller lifting and throwing what another has thrown in front of him. 12 THE SCIENCE OF ROAD MAKING. •lyooj Suui'Bd -aj pn« Jguidas^i joj psppB sq 6} ^unoiuv -« -P ■"h '^H ^H '^S suoSbai jo s^jbd ui puoj o; pjwit Diqna jod ^so^ •SMOJJTjqpaqAv UI p'BO[ o; pjBiC DiqnD aad iso^ •uasooj o; pjBiC 3Tqn3 aad ^soq -P H|ao TH|ce th|oo I |l-( JTl |t-I -f^. ^t ' TH|t- ,2 4) >% ^ IS S o S S If •§§ I- O cj o "tl ""^ O O s; "* o o IS . o fl ^ ^% o 0) o s ^ rt o 'o C/3 C3 U2 .s ii §1 a P o ^ o o ^tS 2 M "z; o •aaquin^.^ « t^ THE SCIENCE OF ROAD MAKING. n Wheelbarrows. — The usual distance of transport suitable for the use of wheelbarrows is 100-200 feet. In exceptional cases it maybe more, but perhaps never above 500 feet and then only for mode- rate quantities. In going up hill, the greatest inclination is to be not more than i m 10, and a man can push only ^ as much on this in- clination as on a level. 3 feet vertical transport costs as much as 90-100' horizontally. Whenever possible, planks should be laid for the wheel-barrows to run on. The best timber for this purpose is beechwood and the cost of keeping such planks is only about -^ or -^ per. cent, of the cost of transport per cubic yard. Distance of Transport in Feet. trips per n hours, one man and one -^3 ubicyds. be trans- le cost of r's day's er of of te ewith xrrow, ad. Ill erofc ;hcan edattl labore es. umb day mad atb tolo %n umb whi< port one wag 7\ ^ iz; 120 ^% 23.5 1 10 2K 16.9 100 2>^ 14.4 98 ■^Yz 13.8 96 ^Vz 13.3 94 '^Yz 12.8 92 ^Yz 12.4 90 ^Yz 12.0 88 ^Yz II. 6 86 '^Yz II. 2 84 '^Yz 10.9 82 '^Yz 10.5 80 ^Yz 10.2 10-20, 20-50, 50-70, 70-100, 100-150, 150-200, 200-250, 250-300, 300-350, 350-400, 400-450, 450-500, 500-550, Patent Portable Railroad and Hand-Cars. These have lately been introduced in this country, and appear to be coming into general use and favor. The company owning this improvement, as it seems to have a right to be called, claim, that by means of their track and cars, which can be used everywhere that a wheel-barrow or a horse-cart can go, and in a great many places where these vehicles cannot go, they affect a very large saving, as much in some cases as f of the cost by the other means of transport. There are no data published as yet to make tables from, similar to the foregoing ; from the company's pamphlet, however, one given case which occured on Staten Island in 1867, may be analyzed and tabulated as follows: — H THE SCIENCE OF ROAD MAKING. Distance of transport, in feet, . . . • . 550 Number of trips per day often hours, with one man at two cars, and two to load, . . , . , 150 Contents of car in cubic feet, ..... li«34 Number of cubic yards which can be transported at the cost of one laborer's day's wages, . . • • 60 One-Horse Carts. The table for this kind of transport may be stated about as fol- lows. I foot vertical costs as much as 14 horizontal. made hours, y four load, r trip. "K . icyds. trans - e cost day's a|§s^ '^1 i-^^-s Distance of Transport in feet. 'S's^..^ or, •Ss^g o> of per day assumi minute dump, ^3 umber which < ported of a lab wages. ;? P? 300 86 8 17. 1 500, 67 8 13.6 1,000, 43 8 8.6 1,500 31 8 6.4 2,000, 25 8 5.0 2,500, 21 8 4.3 3,000, 18 8 3.6 Ox-cart transport is 10 or 12 per cent, cheaper than the above, but takes more time. Other methods of transport, such as horses or engines on tem- porary tracks, would hardly ever be applied to road-building, but belong more properly under the head of railroad construction. , Shrinkage. In calculating the cost of earthworks, the so-called shrinkage of earth must not be overlooked. Earth occupies on the average -^-^ less space in embankment than it did in its natural state, 100 cubic yards, shrinking into 90. Rock on the contrary, occupies more space when broken, its bulk increasing by about one-half. The shrinkage of gravelly earth and sand may be taken at 8, of clay 10, loam 12, surface soil 15, and of "puddled " clay 25 percent. The increase of bulk of rock is 40 to 60 per cent. THE SCIENCE OF ROAD MAKING. To make use of all these data in calculating the probable cost of a piece of road, there are of course still wanting the equally essential factors which give the number of cubic yards to be dug and moved and the distance of transport. These are got from the plan, profile and cross-sections of the proposed work, an engineer's knowledge being requisite to make the necessary drawings and calculations. Drains and Culverts. The drainage of roads is of two kinds, surface and sub-drain- age. The first provides for a speedy removal of the rain-fall on the surface of the road and the cutting and embankments on which it is carried; the second, for the removal of that part of the rain- fall which nevertheless does penetrate into the body of the road- covering. With a perfect sub-drainage the winter's frost, having no water to act upon within the body of the road, is robbed of its great power to destroy the same, and it also prevents the road-surface from becoming soaked and thence destroyed in the summer. The need of surface drainage is self-evident. This last named is to be pro- vided for at this stage of the building of the road, the sub-drainage be- ing more properly a part of the building of the road-covering or top. For this purpose ditches, one on each side generally, are absolutely necessary, both when the road is on a level with the surrounding country and when it is in a cutting. They may become necessary also in the case of embankments : for example, when an embankment is built across wet ground. Where these side ditches cross under the embankment we have a culvert: also whenever any small valley, having a constant or intermittent stream of water, is crossed by such an embankment. It is very bad policy to make such culverts of wood, unless indeed they are so situated as to be constantly under water; the cost of replacing them after the embankment and road has been built over them is disproportionately great. They should be made of stone, or brick; lately vitrified stone-ware, or cement drain-pipe, oval or egg-shaped, has been used to advantage in their construction. All ditches, drains and culverts should have a fall throughout their entire length. Their size will depend on the amount of water they may be expected to carry, and this again on the rain-fall that wiay occur on the area which they drain. Extraordinary showers l6 THE SCIENCE OF ROAD MAKING. have occurred of 2 inches in half an hour but only over a very limited area, and 2 inches in an hour may be taken as a large allowance. This is the basis of the Central Park drainage calculations, and is larger than usually taken, none too large however for safety. The determination of the proper width and height of culverts, that will enable them to pass the requisite quantity of water with- out damming it up, is a question in practical hydraulics, easily enough settled, in cases of doubt, by the proper gaugings and observations made upon the spot, but which is answered only in a very crude and imperfect manner by any general rules that may be given. And yet it may prove a very important question at times. There is now (1877) pending in Massachusetts, a suit for damages, that may involve claims to the amount of rising half a million dollars, in which one great centre of attraction is nothing but a simple railroad culvert, and the question : Was it as large as it ought to have been ? and the ^writer passes every day, when at home, by a culvert, which for some 150 or 200 years has dammed the waters of a brook back about 3 miles, from i ft. to say 20 in. at the culvert vertically, and done this right along two or three times per annum, and at the present time it contributes in this manner, more than its proper share towards the flooding of about 500 cellars. These two cases may serve to call attention to the great damage that may accrue from making culverts too small, and to show whence comes the rule : in cases of doubt, make the culvert plenty large enough. The following rough ancf lapproximate rules for determining the quantity of water that a cul- vert will be called upon to pass through it, are taken from a Ger- man pocket-book for road engineers. Compute the cubic feet pel second from the drainage area that lies above the culvert, and, foi the different lengths of valley from the corresponding rain-falls per hour. (The rain-fall is given in inches per hour, instead of in decimals of a foot per second, only for the purpose of avoiding the j)rinting of long decimals). LENGTH OF VALLEY IN MILES. INCHES PER HOUR. 2 . 5 or less, i . 2 2.5 to 5. 0.75 5. " 7-5 0.45 7.5 "10. 0.30 10. or more, 0.15 As culverts grow larger and wider with the amount of water they -are to pass under the road, they develope finally into Bridges. Bridge-building is a life's study, taken by itself, and in some of its parts it is not half appreciated and known as yet among the pub- lic. Prominent among these is beauty of design and appropriate- ness to the situation. There is perhaps nothing else that will so THE SCIENCE OF ROAD MAKING. 17 much improve the appearance and attractiveness of a road as a beautiful bridge. So also in cities w^e find that a street vs^ill of its own accord, seemingly, improve in appearance, v^hen a good and handsome bridge has been erected on its line, the owners and build- ers of the adjoining buildings taking the bridge for their pattern and model. Nor must it be supposed that a handsome bridge must ne- cessarily cost more than an inappropriate or homely, uncouth struct- ure ; it need never be the case. Very often the chief beauty of a struct- ure lies in the fact of its carrying the most with the least expenditure of material. No one bridge is proper in every situation, and herein many mistakes are made. The correct way to build a good bridge, is the same or a similar way to that followed in first-class buildings, namely, to have plans drawn for the same and receive estimates and offers to build according to these plans. It is not well to allow the offices of designer, superintendent and contractor to be united in one person or firm, and is expecting too much from human nature. Making the Road Surface. There are two subordinate kinds of road surface, if the term road can properly be applied to them, namely, that of foot and riding paths ; these may be disposed of first, before proceeding to the more important consideration of the road surfaces proper, those used by vehicles of all descriptions. Footbaths. — For the surface of a foot path little solidity is ne- cessary, except in city sidewalks, which are not supposed fo be treat- ed of here, but we do need a material that shall become and stay compact soon after it is laid. Coarse sand, screened gravel, stone chips and dust, make good paths ; should these materials be too free from any earth or clay, a little of the same may often be added to advantage to act as a binding material. Wherever the ground un- derneath the surfacing is not porous or likely to remain porous enough to let all the water that may soak through drain away, a layer of such porous material must be filled up before the top sur- face is put on. Oyster shells, or large stone chips, gravel stones or pebbles, etc., make a good foundation of this sort. The top cover- ing should have a slope, best in both directions from the centre of the path towards each side of about i in 16; the thickness of the foundation course to be 3 to 5, and that of the top 3 to 4 inches. 1 8 . THE SCIENCE OF ROAD MAKING. No gravel path, or side-walk, will afford good walking at the season of the year when the frost is coming out of the ground. Carting on more gravel is in vain ; it is often no better than mere foolishness. If village communities will get this idea firmly into their minds, and, instead of a fruitless struggle against the laws of nature and of gravel, will build stone screening sidewalks with a good foundation course underneath, as above described, or else some sort of hard sidewalk covering, they will save themselves much ex- pense, many muddy feet, and no small amount of consequent and annual discontent, not to say profanity and ill feeling. Heavy rolling and wetting down will save much time in finish- ing the whole process; the roller should be used unsparingly and throughout the whole construction of the path, on the foundation, as well as on the top. Riding-Paths. — From the nature of the travel these are intend- ed to acommodate, their surface must be of a peculiar kind. Inas- much as a horse, in galloping, tends to throw the soil he treads on backwards with his hoofs, the surface must be kept somewhat loose and soft to make riding on it easy and agreeable. This requirement makes it impossible to have any slope on the surface (the loose material would wash away if there were any), and hence we must rely here wholly on sub-drainage, and not attempt any surface drainage. The top is made of coarse sand, free from clay or other binding material, laid on two and one-half to three and one-half inches thick, and spread out level. Under this is a solid foundation, about four inches thick, made of coarse gravel and clay, and having a slope of about i : 20, so that the water will run oflf along its top surface to either side, where it must further be dis- posed of by drains or ditches. In case of riding paths too wide to be so simply built, the sketch shows the method to be used. The foundation is made in several slopes, at the lowest parts of which are placed drains, running in the direction of the path, but commu- nicating from time to time with the sides of ditches or drains. Should, however, the ground underneath be porous enough, the drains may be dispensed with ; and if in their stead holes be dug along the lowest lines, marked fl, a^ and these filled with large stone, the water will, through them, drain away into the ground. Roads, — To make a good road surface is a very simple operation THE SCIENCE OF ROAD MAKING. If after it is only once understood, and, the fundamental principles thereof once comprehended, they can hardly be forgotten. Every- thing connected with the construction, the use and maintenance of roads, was, in times past, before the invention of railways, the sub- ject of exact observations and experiments, many and varied in char- acter. Old engineering works that treat of road-making are on this account excellent reading upon this subject at the present day. Upon road construction no less than upon the need of better road- legislation. Some, perhaps the most of the evils we suffer, in the shape of bad common roads, are merely the result, the necessary consequence of our bad systems of common road management, which are derived from our antiquated legislation upon that sub- ject. Legislation of thiskind has changed but little in a hundred years, and is producing the same evils to-day, that it did a hundred years ago. Hence it is explainable, that the complaints concerning bad roads, and bad road management which we read in books of fifty and of sixty years ago, sound to our astonished ears as though they had been written but yesterday. On this subject may be consulted: The life of Telford, the great English road builder, who died some fifty years ago, (also among " The Lives of the Engineers," by Samuel Smiles), " A treatise on Roads," by Sir H. Parnell, 1833, and other works of former date. Besides this, we have the results of a great number of years of experience in older countries, and there would seem to be little to invent, but much to learn, in this branch of construction. Though less progressive than other branches, there are nevertheless im- provements in road-making, especially in road-making machinery and tools ; and no treatise on this or any other living subject can be considered complete in a very few years after it is written. Ancient roads were made with a surface as nearly resembling the solid rock as possible. So, in China, roads were made of huge granite-blocks laid on immovable foundations. In time these be- came worn with ruts, especially in the joints or seams of the stones, and the surface generally so smooth that animals could hardly stand, far less trot on it. They are now for the most part deserted, and left to be covered by land-slides, etc., to one side of the new roads of travel. The invention of McAdam consisted in having no large stone at all on the roadway, but having it all pounded into fragments and spread over the road-bed. This has, without fear of efficient con- tradiction or shadow of doubt, been proved by trial to be a worth- 20 THE SCIENCE OF ROAD MAKiNG, less proceeding, though at one time popular, ainl eve© now too often done, either from ignorance or laziness. The separate frag- -ments of stone, have no bond among themselves, are liable ^o sink ^into the underlying ground or road-bed, evenly or unevenly as' ** may chance, more in one place than another, and thus never, come to rest or to an even top surface. Between these two extremes of an ancient Chinese solid rock road and that of McAdam, lies the true principle of road-making, which consists in giving every road two component parts ; one, — the foundation, — to be solid, unyield- ing, porous, and of large material; the other— the top surface — to be made up of lighter material, and to be made to bind compactly and evenly over the rough foundation. This constitutes the whole principle to be followed; and let it be repeated, that to dump the road material directly on the ground, without first preparing a foundation for it, as is so frequently done, is a waste of time, labor and materials, by no possibility resulting in a good road. On this one fundamental idea, which is never abandoned, however, there are a number of variations. Besides these roads, whose character- istic is the foundation they are all built on, we have paved roads, or pavements, of a great many kinds, and roads with trackways, also of various kinds. Foundation Roads. The roads of this kind, with macadam for the top surface, are called Telford roads by English writers, from Telford, who first built them in England. The Central Park " gravel roads " belong under this head, gravel taking the place of the macadam of the Tel- ford roads. These foundation roads are of far greater importance than any other kind for State, county or town roads, also for parks and driveways. The top surface of all these roads must have a certain inclination, to cause eflficient surface drainage. Various authorities give various rules for the amount of this inclination or side-slope. It would seem just that it should depend on the nature of the top covering, being less for more solid than for looser or softer materials, and also on the grade of the road. In Baden, one of the smaller German States, but which is worthy to be taken as a model in matters of road-building, and in France, the rise at the centre is given as ^--^ of the width of the THE SCIENCE OF ROAD MAKING. 21 taad, according to the nature of the material ; that is, inclinations of I in 20, and i in 30. The rules in Prussia prescribe inclinations of 1 in 24 for roads falling more than 4 in a hundred; i in 18 for roads on a grade of between 2 and 4 in a hundred; and i in 12 for those on a grade of less than 2 in a hundred. When first built, the cen- tre should be made some four inches too high, to allow for after settling. Macadam Top. — The cross-section of such a road is about as drawn; *™° |^^^^^^^^^^^^^^^ the thickness of the foundation b^=za., the thickness of the top covering at the centre, and is six, four or five and three and one-half inches in thickness for first, second and third class roads. If the stone for the foundation — for which most anything will do, and that kind should be taken which is cheapest to procure — happens to be got out cheapest in larger pieces than the above dimensions, it will do no harm. This foundation course is sometimes set so as to present an inclination on top, and the cover then put on of a uniform thick- ness over the whole breadth. This is perhaps best, but is some- what more expensive. It will do, in nearly all cases, to set the foundation course on a level, or as near so as the stones will allow, ■nd then make the top crowning, by making the covering say three-quarters of an inch or an inch less thick at the edges than in the centre. The stones forming the foundation should not be set in rows, nor ever laid on their flat sides, but set up on edge and made to break joints as much as possible; that is, set up irregularly. After they are set up, the points that project above the general level may be broken off, and the interstices generally filled with small stone. More or less care and work are necessary in this part of the operation, according to the importance of the road and the depth and character of the material used for the top covering. To roll the road at this stage is to be recommended ; afterwards it be- comes a requisite. The point never to be lost sight of, is that this foundation course must remain porous, must be pervious to water, go that all rain-water that shall soak through the top covering will find, through it, means of escape to the ground underneath ; thence, •ccording to the nature of the subsoil, it is left either to soak into the ground, or must be further led away by appropriate drains. 22 THE SCIENCE OF ROAD MAKING. Of very great importance is the material used for the top or road covering. In the order of their value for macadam, we have. I. Basalt. II. Syenite and Granite. III. Limestones. IV. Sandstones. It will be evident, that a much greater quantity of the soft stones would be required to repair a certain road, than of a harder kind, and on a road lying out of the way of a hard stone quarry or deposit, the question will arise which is cheapest, to pay more for the raw material and get good stock, or pay less and use the worse? There have been some interesting results in places where this matter has been the subject of experiment, continued for a number of years. Thus, on a road in Baden which was formerly macadamized with rock costing only fifty cents per cubic yard, \% Fig. 5. Perspective View of New Pattern Crusher. was finally found cheaper, to take harder rock from a distanot costing one dollar and seventy-eight cents per cubic yard, the salv- ing being both in less quantity of material used and less labor y^» quired in repairs. Just where the limit is, must be found in each THE SCIENCE OF ROAD MAKING. 23 case by long continued experiment, which is well worth the trouble to make, both to save expense and also to have the best possible road, the harder material making a road better at all times, at the same or less cost. After the right kind has been determined, none other should be mixed with it, and should any inferior piece acci- dentally or designedly get into the stock to be broken up, it should be picked out and thrown aside. The stone is broken up into macadam, either by hand or machinery. Wherever any consider- able quantity of macadam is in present or future demand, a stone- breaker is certainly a saving over hand-labor, though it is difficult to draw a line exactly, where hand-labor or machine labor is cheapest. Probably no town that pretends to keep thirty or forty miles of road in good repair, ought to be without one of these labor- saving machines. Those most in use are made by the Blake Crusher Co., of New Haven, Conn., and the following is taken from their circular. Their machine has been patented in the United States and in several foreign countries, and is now in use in almost every coun- try on the globe. It is simple and compact, and being complete in itself, requires no extraneous support or fixtures. Two patterns of the machine are now sold: the old, or "Lever Pattern," and the new, or " Eccentric Pattern." The figures, and following descrip- tion, refer to the last named machine. Fig. 5, is a perspective view of the machine, entire. The frame which receives and supports all the other parts, is cast in one piece, with feet to stand on the floor or on timbers. These feet are provided with holes for bolts, by which it may be fastened down if desired; but this is unnecessary, as its own weight gives it all the stability it requires. The flywheels are on a shaft which has its bearings on the frame, and which be- tween these bearings, is formed into a short crank. On the same shaft is a pulley, to receive a belt from a steam-engine or other driver. Figure 6 shows a side view or elevation of the parts in the machine in place as they are presented to view through the side of the frame. The circle D, is a section of the fly-wheel shaft, which should make from 225 to 250 revolutions per minute. The circle around D is a section of the eccentric. F is a pit- 24 THE SCIENCE OF ROAD MAKING. man or connecting rod, which connects the eccentric with the tog- gles G, G, which have their bearings, forming an elbow or toggle joint. H, is the fixed jaw; this is bedded in zinc against the ends of the frame i^ inch thick. P, P, are chilled plates against which the stone is crushed ; when worn at the lower end they can be inverted, and thus present a new wearing surface. The cheeks I, I, fit in recesses on each side, and hold the plates in place; by changing the position of the cheeks from right to left, when worn, both will have a new surface. J, is the movable jaw; this is sup- ported round the bar of iron K, which passes freely through it, and forms the pivot upon which it vibrates. L, is a spring of India rubber, which is compressed by the forward movement of the jaw, Fig. 6. Sectional View of New Pattern Crusher, with Parts Lettered. FOR Convenience in Designating Pieces Wanted for Repairs. and aids its return. M, M, are bolt holes. B, is the fly wheel. C, is the driving pulley. Every revolution of the crank causes the lower end of the movable jaw to advance towards the fixed jaw about one-fourth of an inch and return. Hence, if a stone be dropped in between the convergent faces of the jaws, it will be broken by the next succeeding bite ; the resulting fragments will then fall lower down and be broken again, and so on until they are made small enough to pass out at the bottom. The readi- ness with which the hardest stones yield at once to the influence of this gentle and quiet movement, and melt down into small frag- THE SCIENCE OF ROAD MAKING. 25 ments, surprises and astonishes every one who witnesses the opera- tion of the machine. It will be seen that the distance between the jaws at the bottom limits the size of the fragments This distance, and consequently the size of the fragments, may be regulated at pleasure. A varia- tion to the extent of ^ths of an inch may be made by turning the screw-nut W, which raises or lowers the wedge N, and moves the toggle-block O forward or back. Further variations may be made by substituting for the toggles G, G, or either of them, others that are longer or shorter; extra toggles of different lengths being fur- nished for this purpose. This machine may be made of any size. The builders have pat- terns for some 13 different sizes on hand at the present day. Each size will break any stone, one end of which can be entered into the opening between the jaws at the top. The size of the machine is designed by the size of this opening; thus, if the width of the jaws be ten inches, and the distance between them at the top five inches, we call the size 10x5. '^^^ following table shows the principle facts that relate to the sizes of machines that are used, generally, for the making of road-metal. No. k S I III •I Extreme Dimensions. Driving Pulley. u 2 Oh 1^ Length Bre'dth Height. Diam. Face. 6i% Inches. ft. in. ft. in. it. in. ft. in. inch. 2 10X7 Five, 4339 8000 5 ZVz 38 4 5 2 VA 250 6 $goo *3 15X5 Six. 4700 9100 8 7 5 5 2 4 8 180 9 1035 *4 15X7 Six. 5890 10490 8 7 5 5 2 4 9 180 9 1125 5 15X9 Seven. 6436 13360 6 5 5 5 II 2 6 9 250 9 1234 Note. — ^The amount of /rt? be followed by the towns in the case of their roads. We need then a higher power than that of the towns. It has been previously shown how we need a power that can be held responsible and is somewhat permanent, and to put it all together, we need, to order and maintain our highways, a Massa- chusetts Board of Public Works. For some years it would have its hands full in improving the existing main roads and laying out some new ones, but in course of time, as in the older countries of Europe, its principal business would be the maintenance of the roads. It must be remembered that the Board of Public Works is merely the intelligent servant and adviser of the legislative and executive; whatever sums the legislature appropriates for certain objects, that is taken by the Board and made to yield its most in the shape of work accomplished. Beyond this and keeping its accounts, it has nothing to do with money or taxation. The small state of B^den, a part of Germany, has been hereto- fore mentioned as a mode] in road construction and the care of the same. From a brief history of the roads of that country and their present management, we may take some useful notes. The account is that of the Chief Engineer of the department of "Roads and Hydraulic Engineering," which has this matter in charge and is therefore reliable. " In Baden the condition of the roads has been a subject of great care. Within the last forty-five years many millions have been spent upon them, and experience has shown this expenditure 58 THE SCIENCE OF ROAD MAKING. to be one of those most advantageously spent. As most of the roads are well laid out, and as there are plenty of them, there remains now (1863) mainly the keeping in repair of the roads to be attended to and not to build any new ones. Our endeavor now is, to do this at the minimum of cost. Statistics gathered on this subject, show good results and point out to us the means of arriv- ing at still better ones. The present road law was made in 18 10. That part of the old law which relates to the maintenance of roads is still in force, but that part requiring labor as a road-tax was abolished in 1831, and likewise most of the road police regulations. The appropriation for roads had to be increased 250,000 florins to pay for the abolished road-tax labor and to make up 170,000 florins previously received from tolls, which were also abolished in 1831. The system now is as follows : All town roads are taken care of by the towns. The State merely appoints and pays a road-master, so called, who superintends fifteen or twenty road-keepers and reports on the state of the roads, the reasons for their bad condition, if that be the case, what is needed, etc. The law for second class or county roads was formerly, that when they were of importance to several towns, they had all to help maintain the same. As this gave rise to continual bickering and quarreling, in which the road suffered most, it was changed in 1856. They are now taken care of under the direction of the State and paid for partly by the State and partly by the towns in which they are situated. Most of the roads under this head are those which have risen in importance since the building of railroads, and are generally those that lie per- pendicular to the direction of the railroad they are influenced by. The towns not having the means very often to properly improve and repair such, it was found necessary and expedient to give them the aid of the State, and in order to procure the necessary funds, all roads that run parallel to railroads and all those that had lost their importance by the construction of railroads, were in 1855 stricken from the list of state roads. These latter as the name im- plies, are wholly under the care and kept up at the expense of the State. In 1835, the total length of the State roads was , . 1,430.8 English milet la 1855, " " " " . . 1,500.8 THE SCIENCE OF ROAD MAKING. 59 Country. Year. Baden. 1871. Prussia. 187I. France. 1872. Hanover. 1871. Massachusetts. 1875. In 1855, by excluding several State roads, this last length English Miles. was reduced to . 1,142.4 '• In 1861, it had increased to 1,190.0 " Second class Roads {heeping fartly faid for by State.') In 1835, the length of these was 467.6 English miles. In 1861, " •• 630.0 " So that the State had, in 1 861, in all, 1,820 English miles of road to maintain, the towns helping to pay on six hundred and thirty miles thereof. The areas, population, and population per square mile of Baden, Prussia, France, Hanover and Massachusetts, according to recent census, are as follows: Area, sq. miles. Population. Pop. per sq. mile. 5,?9I. 1,461562. 243. 134,045. 24.643,698. 184. 204,088. 36,102,921. 177, 14,857. 1,963,080. 132. 7,800. 1,651,912. 212. Baden did have, at a time when her population per square mile was less than it is now, and Prussia, France, Hanover, and many other countries that could be named, have now got, and for the past ^^o or 50 years have had, a system of common road management and resultant common roads, of the character above described; while Massachusetts with a population of 212. per square mile, and corresponding wealth, and others of the States of the Union, have a species of highway management, and its resultant and corres- ponding sort of highways, which, in thinking of the roads of the countries named, are but as evidences of a partial civilization. " The statistics of the road repairs are kept in the following manner. The road-keepers are required to keep a record of all draught animals that pass in either direction. Horses that are being ridden, animals not before a vehicle, and teams going to and from the fields, are not counted. These records are kept only dur- ing the working hours. Likewise, not during the whole year, but only four months in each year, so selected as to give an average amount of travel. The travel on the road on Sundays and out of working hours is taken from a few observations; it is a very small percentage of the whole. At the end of the year these records and observations are collected and graphically represented on a map of the whole State. The different roads are drawn of a dif- ferent thickness of line, according as the amount of travel on them is greater or less. The quantity of road metal used per yard of 6o _ THE SCIENCE OF ROAD MAKING. road, and the kind of metal used, give the data for another such, map, in which the different colors of the roads represent the differ- ent materials used in their repair, and the figures on them and their thickness show the number of cubic yards per mile required to keep the road in order. Finally, we have a third map, which indi- cates, by the thickness of the several lines representing the roads and by the figures on them, the total cost per mile of repairing the road one year." With this picture of a country happy and prosperous, in the possession of good and well-kept roads, it may be well to leave the subject. Massachusetts wants for her proper development, much better roads than she now has; and, reckoning for a period of say fifty years, she can have these good roads, and have them kept in order, at a less cost than that of keeping up the present poor ones for the same time. Besides this, we should see in the one ease a healthy state of internal convnunications and trade; in the other an absence of both. Let each citizen so act and do his part, that these benefits. may accrue to the Commonwealth. THE SCIENCE OF ROAD MAKING. 6 1 APPENDIX. For the sake of arriving at some practical end, I have requested the gentlemen to whom the prizes for essays were awarded to sug- gest what form of legislation would be desirable as a change from our present inefficient system of road management, to one which should promise better, more economical and more satisfactory re- sults. The large and varied experience and observation of these gentlemen, all of whom are competent engineers, entitle their opinions and judgment to favorable consideration ; and the follow- ing, submitted by them, may serve as a basis or outline for future legislation. C. L. F. AN ACT FOR THE MORE PERFECT CONSTRUCTION AND MAIN- TENANCE OF THE Common Roads or Highways through- out THIS Commonwealth (Massachusetts). Sec. I. Establishes a body to be known as the State Board of Highways and Bridges, to consist of three skillful civil engineers, or persons practically expert in the science of road-making, to be appointed by the Governor with the advice and consent of the Council, and to have their office in the State House. Sec. 2. It shall be the duty of the Attorney- General, person- ally or by his deputy, to give his council and opinion on such mat- ters as he may be called upon by the Board, for which service his ■compensation shall be Sec. 3. The first appointment of members of the Board of Highways and Bridges shall be made on or before , and there shall be appointed one member each for the terms of one, two, and three years; after that there shall on or before each year be appointed one member for the term of three years. Sec. 4. Each member of the Board shall receive an annual salary of dollars; give bonds for the faithful discharge of his duties; pay over all moneys, papers, etc., at the expiration of his term or when ordered by the Governor and Council. Sec. 5. Board are to elect a president and treasurer, and make their own by-laws. Sec. 6. A majority of the Board constitutes a quorum; records to be kept of all the proceedings; copies of all plans, estimates, etc., 62 THE SCIENCE OF ROAD MAKING. to be kept; report to be rendered on or before each year, or when required by the Governor and Council. Each mem- ber authorized to administer legal oaths. Sec. 7. Said Board shall prepare and submit to the legislature a plan for the systematic classification of all the highways and townways in this Commonwealth into two or more of the fol- lowing three classes: — Class I. State roads, to be controlled and maintained wholly by the State. Class 2. District roads, to be controlled and maintained by the State, but the expense thereof to be borne by the towns and cities of the districts in which said road shall lie, and the State, in such proportions as said Board shall apportion. Class 3. Town roads to be controlled and maintained as now provided by law. The construction of new roads, of the three classes above speci- fied, to be done as follows: — Class I. State roads, to be laid out and built by the State, through the Board of Highways and Bridges. Class 2. District roads, to be laid out, etc., by the county com- missioners, as now provided, but the board to have the final ap- proval or disapproval of the proposed plans and profiles for said road, and also to have the charge and superintendence of their con- struction. Parties aggrieved by the refusal or neglect of county commis- sioners to lay out a road, to have the right to appeal to the Board of Highways. Class 3. Town roads, to be laid out and constructed as now provided by law. Sec. 8. The paying of road taxes by labor is hereby abolished, and all road taxes are hereafter to be paid in cash. Sec. 9. Board shall have the special charge and superintend- ence, subject to the laws and resolves of this Commonwealth, of all the highways and bridges, and the public works appertaining thereto, which are or shall be executed or maintained, wholly or in part by this Commonwealth. They shall also perform such other duties as may be required of them by the general court or the Gov- ernor and Council. Sec. 10. Whenever any highway or bridge, or public work ap- pertaining to these two, shall come partly within the province of this Board, and partly within that of any other State board, already constituted, then such subject shall be discussed and decided upon in a joint convention or conventions, composed of equal numbers of this and the said other State board, and some member by them chosen as presiding officer. Sec. II. All applications or propositions for improvements 01 new works, of the kind specified in section nine as coming within the province of this Board of Highways and Bridges, and intended to be laid before the legislature, shall hereafter be first made to this THE SCIENCE OF ROAD MAKING. 63 Board. Upon receiving such application, Board shall investigate same, and if they find such v^ork necessary and proper, shall thus report to the legislature, w^ith an estimate of the expense thereof; if they do not approve of such application, they shall report the reasons for their disapproval. The Board may also, in like manner, recommend, whenever they think proper, any improvements of the kind above specified, though no application has been made therefor. Sec. 12. It shall be the duty of the Board to procure for the legislature full plans and estimates of contemplated v^orks or im- provements w^hen so ordered by the legislature. Sec. 13. Whenever any w^ork shall have been authorized or ordered by the general court and the money appropriated therefor, Board shall advertise for proposals for doing said work; plans and specifications of the same first to be placed on file in office of Board, which plans and specifications shall be open to public inspection; advertisement to state work to be done and to be published ten (10) days at least. The bids shall be sealed bids, directed to Board and accompanied by bond to the Commonwealth signed by bidder and two responsible sureties, in sum of two hundred ($200) dollars, conditioned he shall do the work if awarded to him, in case of his default to do so, forfeits, &c. Bids to be opened at time and place mentioned in advertisement. Sec. 14. All contracts shall be awarded to the lowest responsi- ble bidder and who sufficiently guarantees to do work under super- intendence and to satisfaction of Board; provided that the contract price does not exceed the estimate or such other sum as shall be satisfactory to Board. Copies of contracts to be filed with state auditor. Sec. 15. Board reserves right in contracts to decide questions as to proper performance of work and meaning of contracts; in case of improper construction may suspend work and relet the same; or order entire, re-construction; or may relet to other contractors and settle for work done, &c. In cases where contractor properly does work, 'Board may in their discretion as work progresses, grant to said contractors estimates of amount already earned, reserving fifteen per cent, therefrom, which shall entitle holder to receive amount, all other conditions being satisfied. Sec. 16. In case prosecution of any public work be suspended, or bid be deemed excessive, or bidders be not responsible. Board may, with written approval of governor, where the urgency of the case, or interests of the Commonwealth require it, employ work- men to perform or complete any work ordered by the legislature : provided, that the cost and expense shall in no case exceed the amount appropriated for the same. Sec. 17. All supplies of materials, &c., when costing over five hundred ($500) dollars, to be purchased by contract, subject to same conditions as letting out work. 64 THE SCIENCE OF ROAD MAKING. Sec. 1 8. Whenever Board think necessary, for interests of the Commonwealth, to protect same from damage or loss, shall report thus to governor and council and reasons for same, asking power to give contracts without notice required above, and governor and council may grant request, provided three-fourths vote for it. Sec. 19. Whenever Board is of opinion a work may be done tetter without a contract, shall so report to legislature, and they shall procure machinery, materials, &c., hire workmen, &c., to do said work, whenever so authorized by the legislature. Sec. 20. All contracts and bonds by Board to be in the name of the Commonwealth. Sec. 21. No member of the Board to be interested in any con- tract; all contracts made with any member interested, governor may declare void, and shall remove such member so interested from office. It is the duty of every member of the Board and every officer of the Commonwealth to report any such delinquency, if discovered. Sec. 22. Board shall be empowered to employ such engineers, clerks or other assistants, as shall be provided for by the legislature. Sec. 23. Board shall, on or before every year, submit to the auditor, by him to be presented to the legislature with his annual estimate, a statement of the repairs and new work needed for the current year, and of the sums required by the Board there- for; report to be in detail; all sums appropriated therefor to be in- cluded in the annual tax-levy. Sec. 24. All moneys to be paid to any person out of moneys so raised, shall be certified by president of Board to auditor, who shall draw warrant on treasurer therefor, stating to whom payable and to what fund chargeable; such warrant to be countersigned by president ot Board. Sec. 25. Board to keep accounts, showing moneys received and spent, clearly and distinctly, and for what purpose. Accounts to be always open for inspection of auditor or any committee appointed by the legislature. THE CONSTRUCTION AND MAINTENANCE OF ROADS.* The writer wishes to give the Society some statistics and suggestions regarding the construction and maintenance of wheelways, partly drawn from his experience in charge of such work and from observation and information acquired in this country, and recently in London and Paris. Earth Roads. In the construction of an earth or gravel road the effort should be to keep the material near the surface as nearly homogeneous as possible, that the surface may be uniformly hard. The upper layers at least should be thoroughly rolled in thin layers, with sprinkling, if the material is too dry to pack well. The most efficacious roUei for this purpose is of two sets of disks, one about eight inches less in diameter than the other, placed alter- nately on the axis of the roller. It is understood that the cost of com- pactmg reservoir embankments with this roller is about three-fourths of a cent per cubic yard. The writer has never seen it used in road mainte- nance. When the soil is sandy but little can be done besides covering it with some more tenacious material. Clay, or clay hard-pan, is the best, unless a sufficient coat of gravel can be afforded. Even a clay road, if the traffic is not too heavy, can be kept in a firm state by careful and continuous maintenance ; a coat of sand or hard-pan is, of course, desirable. The plan often pursued of repairing roads once or twice a year is not economical, for the dilapidations increase in a heavy ratio after they com- mence. A fair average for re-forming a mile of old road 30 feet wide between gutters, where the material was mostly cast from the sides, was 164 days, 10 hours each, of laborers, and two days of a double team hauling earth, carrying away stones, and moving tool-box. The use of a railroad scraper would have been an economy. Maintenance is most economically performed by double teams, with hones or scrapers, rollers, and the watering-cart in dry weather. The hone or scraper is often an oak plank, 2 inches thick, 10 inches broad, and *By Edward P. North, C. E., Moniber of the Society, read before the American Society of Civil En^neers, April 16th. 1S79. 66 CONSTRUCTION AND MAINTENANCE OF ROADS. 9 or lo feet long, shod on its lower edge with a )i-vciz\i plate of iron, Drawn vertically along the road either by a tongue or a chain — in the first case it has two handles like plow handles — in the second it has a vertical handle, and the earth is dumped by pushing it forward ; a piece of plank about 3 feet long being fastened behind, by riding on which the driver can regulate the amount of earth moved. These are drawn over the road, in- clined 7 or lo degrees from a perpendicular, to the line of travel. So that, besides filling small depressions, they, to a slight extent, scrape the earth to or from the centre of the road. There are also some patented machines, combining a scraper and roller in a frame, which are said to be very effec- tive. 46,000 to 47,000 square yards can be covered in a day, while not more than 2,300 can be put in order if the road is rutted and gullied. While hones are of little use on muddy roads, they are effective just as it is drying. The ordinary type of roller has 6 rings, the whole length being 6 feet, and weighing about 2 tons, with frames that will hold lyi tons of stone. A better is of 2 rings, 3 feet long, also weighing 2 tons. Another is figured in Clemens Herschel's Prize Essay on Roads, and in General Giimore's Roads, Streets and Pavements. The roller should follow the re-forming of the roadbed, whether with hones, shovels, or the ordinary railroad scraper. The writer has rolled earth roads with a 15-ton steam roller, but not enough to be certain as to its economic value ; where the soil contained a fair amount of clay, the roadbed was left very hard, and w^ore well. A water cart holding 60 cubic feet will water 830 to 860 square yards, and can be drawn by an ordinary team over any road that is worth watering. Tvvo sprinklings per day will keep the road in good condition, though not free from dust in hot weather or high winds, if there is much traffic on the road. Sprinkling is the only thing that will keep a road from breaking up in long continued dry weather. The treatment of gravel roads compacted either by traffic or horse rollers, differs very little from that pursued with earth roads. When the gravel is over i inch in diameter, it is almost impossible to keep the road- bed from breaking up when dry, and ^ inch would be a better size, unless continuous watering can be depended on in dry weather. Small gravel (and the same remark applies to metal for Macadam) makes a pleasanter road for travel, and can be more easily kept in order. St. Nicholas Avenue, which will be mentioned further on, was m.ade from nearly clean Roa Hook gravel, by the aid of a 1 5-ton roller, but with a horse roller it will be necessary to add clay, loam or some softer material, to any hard or clean gravel to act as binding. W. H. Grant, Member of the Society, in his valuable description of the roads of Cen- tral Park, says of Roa Hook gravel, " it being more than ordinarily CONSTRUCTION AND MAINTENANCE OF KOADS. 67 clean and hard, bears an intermixture or adulteraticn of 20 to 25 per cent of inferior material to perfect its binding properties." These roads have a foundation of rubble stone, not so firmly packed as Telford specified, covered with quarry chips and hard-pan, which was rolled with 2-horse rollers, 6 feet long. " This is thoroughly done to prevent the gravel filling the cavities of the rubble bottom, so that its cellular character may remain unimpaired to facilitate drainage." The gravel was applied to two or three successive layers, making a depth of 4 to 6 inches. Each layer was rolled with a 2-horse roller, and the last w Ith one weighing 6%, tons, 5 feet long, giving 217 lbs. per inch pressure. These roads, which were thoroughly underdrained and side guttered, have long been famous for their excellence ; they are pleasanter for light travel than Macadam, and are easily kept in repair, except in wet weather, when they become muddy, and when neglected, the larger pebbles make a rough road for buggy riding. For horse rolling binding should be applied as sparingly as possible, and on the last layer, after it has been compacted, simply as a glaze to hold the stone ; if it contains clay, it should be as moist as possible, not to stick to the roller. The so-called Tompkins Cove gravel, which is much used for en- trance drives to gentlemen's places about New York, is a broken lime- stone, apparently of the cement series. It is usually spread over the road, and compacted by the wheels. The darker colored stone is very pleasant to the eye, and it readily makes a smooth wheelway singularly free from either mud or dust, even when subjected to rather heavy traffic, though it is too friable for economical use in such situations. Its per- formance is so different from that of the ordinary limestones that an analysis is appended : Lime 60,20 Alumina 11.22 Silica ^ feet in front of it. On the Avenue de I'Opera, the centre of which is covered with broken porphyry, the stones presented the same evide-nces of motion on each other, mentioned as seen on the Victoria Embankment. In New York City there arc, including St. Nicholas avenue, 27.99 miles or 921,400 square yards of steam-rolled M-icadam roads, besides the horse-rolled roads in the Central Park and the Twenty-third and Twenty- fourth Wards, of which 17.75 miles or 71 8,200 square yards are on Telford foundations. They were commenced in 1869, and mostly finished in 1876, 74 CONSTRUCTION AND MAINTENANCE OF ROADS. The first had a 5-inch layer of gneiss laid on the Telford, on that a 5-inch course of trap, both broken to go through a 2>^-inch ring. The trap was and is machine broken, and the screen- I ings, /. e., dust and stone that passes 1 _c through a i-inch or iX-inch aperture, are j -| used for binding. At first it was held that these should be used as sparingly as pos- sible, but experience has shown that the roads wear better and have less loose stones on them when the interstices ai e fully filled with screenings, and the size of the stone in the top course is preferably from i to 1% inches. The general practice now is to put on the stones in two courses when the thickness, compacted, is 6 inches or more, and roll the first course until it will settle no more, then add the last course, and after it has settled, screenings are added, at first coarse and then fine, and after thor- ough rolling, the whole is puddled by a co- pious addition of water. This is accom- plished more thoroughly and satisfactorily in hot, dry weather. After the road is pud- dled % X.0 Yz inch of screenings are spread over it, and after drying an hour or so the traffic is turned on. For the old style of construction Sixth avenue, between One Hundred and Tenth street and Harlem River, may be taken as a type, having the materials and courses as above mentioned. It was rolled with Aveling & Porter's 15-ton rollers, of the old pattern, in which the weight is nearly equally divided between the steering and driving wheels, which cover 6 feet, giving a bearing weight of 467 lbs. per inch run. As near as can be ascertained, 24 6-10 hours, at iX miles per hour, were occu- pied in rolling 1,000 square yards, giving ' for the work done 0.553 ton miles per square yard, 2.246 ton miles per cubic yard, and 129.8 trips of the roller over the surface. VAvenue St. Nicholas, which, as mentioned above, was made from Roa CONSTRUCTION AND MAINTENANCE OF ROADS. 75 Hook gravel, had a rubble foundation, and it was intended to have 6 inches of compact gravel, but the foundation settled so that in some in- stances the gravel is 14 inches thick. The practice was to lay the gravel on and wet it thoroughly over night. It was rolled the next day until the water was forced to the surface. A 15-ton roller was employed about 26 hours per 1,000 square yards, besides some horse rolling. A little hard pan was used for binding. The intention was to make a road for ^ast driving, but the surface was as hard as that of a Macadam road, though much smoother. The data for these two avenues depend on the memory of the engineer of the roller, and are approximate only. The Telford Macadam on Fifth avenue has 8 inches of Telford, 3 inches of 2>^-inch trap, 4 inches of 2-inch trap, i inch of coarse screenings, and one-half inch of fine screenings, when completed. The wheelway is 40 feet wide between curbs, with 4 foot gutters on each side, of trap blocks. Mr. F. H. Hamlin, for some time Engineer in the charge of Roads and Streets in New York City, to whom I am indebted for these data, intended, by the use of the 1%. inches ot screenings, to have the road as smooth and pleasant for riding as Avenue St. Nicholas, without the tendency to mud in wet weather. The work was let in two contracts, at $1.30 and $1.49 per square yard. The average time employed setting a square yard of Telford was 20^ minutes. Spreading the stone and screenings, per square yard, i 2-10 minutes. About 58 6-10 hours rolling were given per 1,000 square yards ; and the work done, allowing the effective speed to have been 1% miles per hour, was 1.099 ton miles per square yard, and 4.709 ton miles per cubic yard of compacted material, if there had been no settlement, but there was an unascertained settlement. These roads are maintained by spreading very thin layers of tine Roa Hook gravel over them and watering. The first roads were built with an idea that as small a quantity of screenings as possible should be used, and in dry weather the stones, which become prominent by wear, are liable to kick out ; the fine gravel prevents this, and by retaining water sprinkling is not necessary so often. The fact that the travel concentrated near the gutters, where this gravel, by the action of rain, becomes thickest, in connection with the demands of owners of fast horses, who wished a softer road-bed, led Mr. HamHn to cover one of them with a coating three- eighths of an inch thick, consisting of three parts of coarse sand and one part of strong clay. This has been on the road through two winters and the road-bed is still firm, and it has been applied to others. Under Mr. Hamlin's charge the average cost of maintaining these roads has been 4 2-10 cents per square yard per annum for the labor and material of road covering, cleaning and sprinkling, with incidental repairs / 76 CONSTRUCTION AND MAINTENANCE OF ROADS. and supervision. None of them have been resurfaced with broken stone excepting a portion of the Western Boulevard, the first built, and two or three patches of loo feet or less in length, which cost 46 cents per square yard. It is very difficult to estimate the traffic on these roads. On a fine day 3,000 vehicles may pass over them, while at other times there may be not more than one-tenth of that number. In repairing the Southern Boulevard, mentioned above, the trap broken to go through a 2-inch ring was laid on 6 inches thick in one course ; 38 2-10 uours' roiling was given per 1,000 square yards. Allowing the speed to have been 1% miles per hour, the work done on it amounted tO' 0.859 ton miles per square yard and 5.177 ton miles per cubic yard ; 201 trips were mide over the surface. The Macadam was 15 feet wide, and some of the rolling was on the shoulders, though probably not enough to affect the result materially. The work was done in Jnly and August, and a little less than 0.6 cubic feet of water per square yard (3,5 cubic feet per cubic yard) were used in compacting and puddling. About one-third screenings were added. Those portions of the road that had the most work done on them are now in the best form, after nearly two years with- out any care ; and, generally, the more thoroughly the trap roads were j-olled the better do they wear. It should be understood that there was no counter on the wheels of the rollers, and the speed is the result of estimation, interfering with accuracy in the estimate cf the number of ton miles performed. The rollers used fn the above mentioned works were 15-ton Avehng & Porter's (old pattern), and though they are understood to bear equally on the driv- ing and steering wheels, the writer thought the driving wheels nearly twice as effective as the steering wheels. The superiority of the American Macadam roads is partly due to the greater amount of work put upon them ; the binding, which is of the same hard material as the metaling, almost completely fiJs the interstices between the stones, and the entire mass is thoroughly compacted and nearly homo- geneous. It is only while the frost is coming out of the road in the spring that the stones wear upon one another at all. The process of puddling gives a very smooth, hard, firm surface, resistant alike to wear and the infiltration of water, which is of equal advantage to the stabilfty of the foundation and from a sanitary point of view. By the use of the steam roller the stones are compacted with a small amount of wear to their angles and an entire freedom from mud and dung, their only weak point being that in long-continued dry weather the larger stones are apt to get dis- lodged from the surface, some moisture being necessary for the full cohe- sion of the binding. No amount of wet weather, unaccompanied by frost, seems to injure them, unless mud works up through the foundation, and CONSTRUCTION AND MAINTENANCE OF ROADS. 77 their imperviousness under the most disadvantageous circumstances is well illustrated by the practice of Mr. Hamlin, as cited above. The English roads are rolled less, and the binding, though cheaper in ■cost and the matter of rolling and spreading, is, when thoroughly wet, to a great extent an element of weakness to the roads, allowing a large part of the wear to be internal, and failing to hold the stones from dislodgment, either by the wheels of vehicles or the brooms of the sweepers. When dry it can have neither cohesion nor resistance, its use being confined to the time it is slightly damp. The roads in Paris seemed to be less thoroughly compacted than in London, but the binding was better, and if it had been applied dry, after the stone >\'as nearly compacted, and only wet at the last rolling, it would probably be more effective. As it was, the grain of the sand seemed to have been broken down dunng the rolling of the stone, and as, like the English made roads, the stones move on one another, it must be still more thoroughly ground up. The maintenance of roads in Paris is much more effective than in London. It consists essentially in washing rather than sprinkling them, and sweeping the mud and debris of the surface into the gutters, where it is washed with a copious flow of water, the mud and fine sand going into the sewers, the coarser sand being retained for use on the streets. "Most of the work is done at night and in the early hours of the morning. While there is on the average (judging from the amount of mud relative to the traffic) rather more wear than in London, no loose stones were seen on the streets, except when newly mended, men apparently being always present with brooms, rammers, and sand, to repair any place that showed signs of weakness. On the Avenue des Champ Elysees, and other flint roads, the surface was often swept with birch brooms having long and slender twigs. In London the maintenance is neither so constant or skillful ; the roads are watered in dry weather, and swept or scraped in wet, with an occasional addition of sand or fine gravel. There seems to be no accessible accounts of the cost of repairs and maintenance in London. W. S. Till, the Borough Surveyor of Birming- ham, in one of his reports, says : " Mr. Howell, Surveyor to the Vestry of St. James, Westminster; informs me that the cost of maintaining, etc. the surface of Regent street, London, which may be considered one of the best Macadamized roads in the Kingdom, and in which nearly every description of pavement has been tried, is $0.87 per square yard per annum it has, however, been much higher." It is not known whether Regent street was then steam or horse rolled. In Paris, the expense of maintenance had reached on some of the streets 16 francs per square meter ($2.57 per square yard) per annum, and it 78 CONSTRUCTION AND MAINTENANCE OF ROADS. was resolved to pave all but the middle 23 feet, in streets 48 feet wide, and to pave narrow streets and gutters, and in 187 1 it was resolved to pave streets where the annual expense of maintenance was over 48 cents per square yard, excepting those avenues which are used by carriages of luxury. This, however, was not fully carried out. Many adverse criticisms are made on Macadam roads by parties who judge of their value mainly from reading statements regarding European Macadam. A well-made trap road, when properly watered and main- tained, is, after an earth road, the pleasantest and safest road known. In this locality a road 15 feet wide would give suburban residents the same easy access to their railroad stations in the worst winter weather as in summer. And for streets of residence, where the inhabitants would keep them free from garbage, both for quiet, safety to horses, and on sanitary grounds, they are preferable to the ordinary paving. It is possible that with thoroughly compacted and bound roads, the English and French engineers would look with more favor on Telford foundations, for with the roads we make, the wear between the Macadam and Telford must be very slight, the pressure of a wheel being spread over a large surface. They are preferred here because they give an equa depth of foundation more cheaply than with broken stone, and as in this country municipal appointments of engineers are sometimes influenced by political considerations, the general desire is to build as solidly as pos- sible. One objection that may be urged against the Telford foundation is the fact that it does not have a solid bearing on the earth roadbed, and when the road is worn thin the spaces between the stones may become filled with water and mud, which will work through the foundation into the broken stone, hurrying the disintegration of the road. The English engineers often use "hard core," a mixture of brick rubbish, old plastering and broken stone, on a clay soil, to prevent the mud working into the metaHng. The result was accomplished by the use of six to eight inches of fine sand on Mott avenue, New York, which was built at the joint expense of the city and private parties. The regulation of the s'jrface required a maximum cut of two and a half feet and a fill of four feet ; the soil was a heavy loam, thoroughly saturated by the fall rains, which continued until the work was completed, and it was desirable to Macadamize it immedi- ately. Rough gneiss rock was placed on the layer of sand and rolled to an even surface, with a thickness of about eight inches, and on th^t a scant six inches of loose 2-inch trap, to which thirty per cent, of screenings were added. The bottom was very treacherous ; on about half the road it was not safe to stop the roller, which broke through in two instances in spite of the care exercised. Nor could the road be rolled long in one place ; but CONSTRUCTION AND MAINTENANCE OF ROADS. 79 as soon as the surface began to weave in front of the roller it was given a rest, and the roller taken to another part of the road. In spite of this the fOad was compacted and the surface puddled satisfactorily, except in one or two small patches. It has stood the freezing and thawing of two winters without receiving or requiring any attention. It is held that the success of this operation, so contrary to the teachings of the books, was due to the layer of fine sand being impervious to the mud, which without it would have been over the top of the Macadam a long time before it was puddled. The deductions of the French engmeers from the table cited on page 12 should have been strengthened or modified by a statement of the wear of the different work done. And their principles of road construction are dissented from, because the writer believes that the horse-roller made road does not differ so much (after both are compacted) in wearing value from the road specified by Macadam as it does from the road properly made by a steam roller ; that all binding should be fully as hard as the stone, and that the better road is made with the heavier roller per inch run, as far as his experience has gone, /. e., up to 460 pounds. And, in addition, up to that weight the ton miles rather than the load should be altered on ac- count of the greater or less hardness of the rock employed for road con- struction. It is believed that no one who has used the twa styles of 2-ton rollers mentioned, viz., 3 feet and 6 feet long, doubts that the 3-foot roller will do better work than can be accomplished by the 6-foot roller without leading. Under the writer's direction the same quality of syenitic gneiss men- tioned on page 9 was rolled with a 15-ton steam roller, with binding of the same quality in both cases. There were only about 200 cubic yards of it, and on account of the traffic passing, it was impossible to keep an exact account of the work done, but the road is very satisfactory, and from it the writer thinks that a few passages of the steam roller over the horse- rolled road would add materially to its life, besides greatly reducing the number of loose stones on its surface. Some refuse Westchester marble (a very soft rock) was delivered on some of the roads at about 25 cents per cubic yard, and hand broken in place at the rate of about i cubic yard per hour. A portion was rolled before any traffic went over it, some after about two weeks of traffic and some after six weeks ; of the rest, part was horse rolled and part com- pacted by wheels ; the quality of the stone, traffic, etc., were very nearly the same ; that not rolled by the steam roller soon wore into holes; the first mentioned is, after standing two winters, in very fair surface ; the others decreasing in the order in which they are mentioned. This dif- ference is so noticeable that any one could pick out their sequence as men- tioned. So CONSTRUCTION AND MAINTENANCE OF ROADS. Shortly before this, however, the writer very nearly made a mush of some micaceous gneiss in trying to reduce the crown of a road covered with it. CONSTRUCTION AND MAINTENANCE OF ROADS. 8i Late in the fall a portion of the Southern Boulevard was repaired with 2-inch trap, screenings, and a 2-ton horse roller. After the metal was compacted a thin coat of clay hard-pan was added, which froze solidly that night, and a day or two after was covered with snow which stayed on till spring, thus giving it the most favorable surroundings possible. In the summer there was but little difference between it and the steam rolled part ; but by fall it had commenced to deteriorate, and now its surface is but little better than that made seven years before. Both the English and French prefer hand-broken stones for Macadam. An experienced breaker will make better shaped stones than any crusher can, and hand-breaking would afford employment to labor. The hand- broken stones mentioned above were delivered by contractors at $2.00 per cubic yard ; the men who broke receiving on an average Zi% cents per yard. One man was thought to have broken at the rate of 4.5 cubic yards per day ; about 6 to average 1]/% yards or more. They stood, using hammers weighing 1 1^ to 2 pounds, on very flexible handles. The ave- rage of all who worked could not have been much over i yard per day. On the other hand, there is not enough fine stone for binding, what there is is full of dirt, and machine breaking is cheaper ; the cost of crush- ing trap with a Blake crusher, after it is sledged, being understood to be less than 70 cents. The crown or transverse section of a road should depend on so many different considerations that no general rule can be drawn for it. With Macadam made from hard material, the less crown, on many accounts, the better, as the surface is benefited by being kept damp. In narrow \vheelways, particularly, an excessive crown throws all the traffic, as much as possible, in one line, whatever the material may be. On the other hand, in curbed streets, if the road is too flat, the heavy traffic tends lo concentrate near the gutters. The crowns given to dirt roads are in- tended to drain off the water, but the longitudinal ruts soon defeat that object. Transverse profiles of the Western Boulevard and Sixth Avenue, New York City, are shown on page 80. On the former, tiiough the transverse slope is so slight, it is perceptible to a person riding in a vehicle with longi- tudinal seats, but is not noticeable when on a transverse seat. The cross section of Sixth Avenue shows the surface as the road was constructed by M. A. Kellogg, Engineer, in 1872 and 1873, with the crown at the same height as the top of the curb stones, and the figures above the dotted line joining the curbs show the average distance of the surface below street line, as found by careful levels taken this spring between 123d and 124th streets, a point where no broken stone had been added, the wear at the crown being 0.15 foot, or about ;^-inch per year. The road is not too flat, as it now stands, to shed the ramfall. 82 CONSTRUCTION AND MAINTENANCE OF ROADS. The amount of water the writer found necessary to keep earth or Mac- adam roads from becoming dusty, was, for a well mamtained earth road, at the rate of 71.3 cubic feet per 1,000 square yards, applied twice in a day, or say 143 cubic feet per day. In very hot or breezy weather this was not quite enough. On the Telford roads of this city, 25 cubic feet, applied four times a day, are necessary per 1,000 square yards, say 100 cubic feet per day. One water cart, holding 79 cubic feet, waters 35,000 square yards four times a day, keeping it free from dust, except during windy weather. In Paris about 27 per cent, of the surface is watered by hand hose. These are made of iron pipes about dyi feet long, each end supported on castors and connected with leather or rubber couplings ; the working end being a piece of rubber hose. Its cost is one-half that of watering by carts holding 46 cubic feet. Stone Pavements. The City of New York is largely paved with the Belgian pavement,/.^., truncated pyramids of trap set in coarse sand. The sand soon becomes saturated with the water and mud of the streets, and the blocks working under the traffic become rounded. It is impossible to keep such pave- ments in fair surface, and they are as bad sanitarily as pavements can be. The pavements now laid are of granite or trap blocks, 4 inches wide, 6 inches deep, and 8 to 12 inches long. They have parallel sides, and are laid in sand, probably form'ng the most efficient pavement ($1.91 per square yard), to be found anywhere. The open joints filled only with sand are objectionable, however, as formmg receptacles for street mud and water. The Guidet pavement laid in Broadway, with a foundation of concrete, has lasted very well, its increased wear probably compensating for the ad- ditional cost of the concrete foundation. In Paris, the new pavements are of Gris, a hard sandstone, which is neatly dressed in blocks, 4 to 5 inches square, and laid either in sand or mortar, and porphry, about 4 inches wide, 6 inches deep, and 8 inches long, generally laid in mortar. The best granite pavements are found in England. In London, where the soil is clay, the usual practice is to lay a foundation course of " hard core " which is well compacted by rollmg, &c., and the stones are set on this in two inches cf sand. The better class of pavements, on clay, have 3 to 6 inches of hard core, 9 mches of concrete, and two inches of sand. Col. Haywood, wbere soil is sand or gravel, puts down 9 to 18 inches of broken stone, or 9 inches of concrete, saying that there is little difference in the stability of the two foundations, but the concrete is apt to be replaced in a more satisfactory condition when the street has been opened. CONSTRUCliON AND MAINTENANCE OF ROADS. 83 In all the better class of London pavements, the sets are 3 inches wide, neatly split out with parallel sides, and set in blue lias lime grout, Aber- deen granite being chosen in preference to harder varieties, as it wears rough. Though Col. Haywood determined that the duration of the same stone varied directly with their size, these narrow sets are preferred, as making a smoother road, affording a better foothold for horses, and in- creasing the quietness and general comfort. The practice is to take up the sets when their surfaces become rounded, and redress them, after which they are relaid in streets of secondary traffic. The spalls are useful for foundations and Macadam, Col. Haywood estimates the total life of such paving stones to be 29 years. In Liverpool, Geo. F. Deacon prefers the Welch traps and granites, which are rather harder than our trap. The pavement of North John Street, which has a traffic of 4,000 vehicles, averaging 3 tons each, per day, is of trap blocks, neatly split out, with parallel sides, 6 inches deep, and 3X X3X inches on the face, set on 10 inches of concrete; the joints are filled with gravel, about the size of a pea, free from sand, and then run with coal tar pitch. It had been paved very close, and the sets were so firmly held in place that there was hardly any rounding of the surface last winter, though it was laid in 1872. The surface was admirable, and showed very slight wear, and on sanitary grounds it- is probably unequaled by any other pavement, except compressed asphalte, for there can be no percola- tion of the surface water. The only signs of failure shown by this pave- ment is where the boiler of the " Montana," weighing with its 4-wheeled truck 59 tons, passed over it, crushing some of the sets, and showing that stones 3X inches square on the face, are not large enough to stand loads of 1 5 tons per wheel. Mr. Deacon thinks that the 3X inch square blocks present too many longitudinal joints, and now employs sets 3 inches thick by 6^ inches deep, and 5 to 7 inches long ; the specification for thickness is that any 4 of them, when set side by side, shall measure 12 inches, and not more than 14 inches. It is said the specification is filled without extra cost. Wood Pavements. In London, the principal wood pavements are Gary's, the improved Wood, Henson's, and the Asphaltic Wood. Cary's is laid on sand or gravel, a firm foundation being first made. The patent is for dovetailing the blocks on their ends, which is held by the inventor to give the pave- ment greater stability. The joints are flushed with blue lias lime grout. The advantage claimed for this pavement is the ease with which it can be repaired, the method being apparently to take out the defective block or blocks, cut off the broomed portion that overhangs the sides of the blocks, put in enough gravel to restore the surface, replace the block with the 84 CONSTRUCTION AND MAINTENANCE OF ROADS. other face up, and run in the grout. A portion of Cannon street is laid with this pavement. It is said by persons on the street to require fre- quent repairs. Its power of resisting wear must depend on its founda- tion, and it can hardly prevent water from working into and through the foundation. The " Improved Wood" Company started to make an improvement on the Nicholson patent, using two tarred boards, resting on sand, under the blocks. Ludgate Hill, and some other streets, were laid on this principle, but, under the heavy traffic, the two boards acted Hke a pump, pumping the sand up through the pavement. After trying and discarding one board laid on concrete, they now lay a foundation of concrete 6 inches thick, on which the blocks are placed ; the jomts are filled with pitch and gravel. This modification apparently makes a good pavement, as seen on Ludgate Hill, where the first pavement has been renewed, and at St. Paul's Church-yard. No company now lays boards as a part of its founda- tion. Under the name of Ligneo Mineral Pavement, a company laid some pavement of hard wood, but it proved so slippery that work under that patent has been mostly abandoned. The most work seems to be done, at present, by the Henson and Asphaltic Wood companies. In the Henson pavement the 6 inches of concrete is covered with a layer of tarred felt paper, on which the blocks rest, while a strip of the same material is placed vertically between each row of blocks across the street. Nothing is interposed between the ends of the blocks. After each few courses are laid the blocks are driven close together by a heavy maul. Hot coal tar and pitch is plentifully applied to the upper surface, after which gravel is strewn over it. It will be observed that this pavement pre- sents about as small a joint for foothold as is possible, and to meet objec- tions on this score, at first about every fifth course had a V-shaped groove cut in its top. This has been abandoned by the company, who now lay the surface flush, making a road almost free from noise and near- ly as smooth as a compressed asphalte pavement. In answer to objec- tions to their narrow joints, their engineer asserted that they had changed the practice of the other companies in London from 1% ox \ inch joints to as near a quarter of an inch as it is practicable to make them, to the decided advantage of all pavements. They also assert that the tarred felt under the blocks will not wear out, that the pavement is impermeable to water, and that it can be more thoroughly cleaned than any other wood pavement. This pavement was taken up, for pipe connections, in Leaden- hall Street and High Holborn. Although it had been raining in the first instance, and raining and freezing in the other, the wood was bright and not at all watersoaked ; the felt underneath, however, was considerably worn. The claim in regard to cleaning is probably correct. CONSTRUCTION AND MAINTENANCE OF ROADS. 85 The asphaltic wood pavement, laid under the patent of H. S. Copland, C. E., has on the 6 inches of concrete a quarter of an inch of tempered Trinidad bitumen, on which the blocks are placed ; the joints across the street, which are kept between a quarter and an eighth of an inch, are run with a softer bitumen for about 2 inches, and flushed with lias lime grout, the ends of the blocks abutting against each other ; the whole is covered with gravel. The pavement, unless cracked by the settlement of the foundation, must be as impervious to water as one of asphalte, and should stand the traffic very well. On account of its rigid foundation it is more noisy than the Henson, and having a slightly wider transverse joint, it hardly rides as smoothly after some wear, though the difference would not be readily noticed. It should be noticed that the bitumen which is run in the joints makes a firm bond with the layer under the blocks, and more wood is spoiled in taking up this pavement than any other observed. This pavement was first laid in Cannon street, between Abchurch and Laurence Pountney Lanes, in July, 1874. It was laid, apparently, with joints rather over than under i inch, and in December, 1878, the edges of each block had broomed over into the joint ; otherwise the surface was good, and I could not learn from any source that repairs had been made on it, except when the street had been opened for pipes. The grade is i in 90 ; and in 1873 the number of horses passing over it in 12 hours — from 8 A. M. to 8 p. M. — was 5,350. The practice in London is to cover the surface of wood pavements several times a year with hard gravel, which is beaten into the ends of the fibres by the traffic, tending to preserve the blocks from wear and, it is claimed, from decay. The wood used is a species of pine — Baltic fir — harder than our white pine and softer than Southern or pitch pine, resembling- what is sold in the Chicago markets as Norway pine ; it is better seasoned than the pine generally used by house carpenters ia this country, and it is usually laid without being creosoled, the borough surveyors claiming that the difficulties of inspection are increased by creosoting ; but as far as noticed, for renewals and repairs, which are made by the companies under their contracts for maintenance, creosoted wood is used, their managers saying that they expect it to add to the wearing qualities of the wood as well as to protect it from decay. The concrete, usually covered with a thin coating of cement mortar, is made of one part of Portland cement to six parts of Thames ballast, which varies in size, from sand to pebbles three-quarters of an inch in diameter. It is rather difficult to arrive at the durability of either wood or asphalte pavements in London, as Col. Haywood, the City Engineer, lets them at a certain price, with a provision that they shall be kept in repair for a term of years at a certain price per square yard per annum, a good pavement being turned over to the city at the expiration of the contract for main- 86 CONSTRUCTION AND MAINTENANCE OF ROADS. tenance, the contractor, in the meantime, replacing the entire roadway, if necessary, as will be noticed under the head of asphalte. This plan has worked so well in the city that the surveyors for the vestries have gener ally adopted it, so that, in London, the wood paving contracts are usually let with the same length of maintenance as for compressed asphalte, and at about the same price, viz., at a first cost of from $4.38 to I3.90 per square yard, including foundation, but not excavation. They are kept in repair for two years at the contractor's cost, and at the rate, depending on ^he amount of traffic, of from 36^ to 18X cents per square yard per annum for the succeeding fifteen years. From the report of Col. Havwood to the Commissioners of Sewers of the City of London upon asphalte and wood pavements, 1874, page 38, et seq., we find that the greatest duration of any wood pavement was in Mincing Lane, nineteen years and one month ; the average cost per square yard per annum having been, in that instance, thirty-five and one-half cents, while the average cost of three heavy traffic streets had been sixty- three and nine-tenths cents. He concludes that, with necessary repairs wood pavements will last ten years in London. Law & Clark's Roads and Streets, page 239, gives the wear of three wood pavements at three-tenths of an inch per annum under a traffic averaging 362 vehicles per day of twelve hours for each foot in width of the street. Mr. Clark says it is claimed, in some instances, blocks have worn down in London to a depth of two and one-half inches (the Wells street pavement was only two inches thick, before removal), and suggests eight or nine inches as a better depth than six inches, now universal. The blocks of the Mincing Lane pavement, w^hich lasted nineteen years, were nine inches deep. If we assume that the blocks are six inches deep, and that the road v/ill not break up until they have worn down three inches, there seems no reason why a thoroughly creosoted wood pavement, laid with narrow joints, on a sufficient bed of concrete, wiLh a water-tight stratum interposed, should not wear for about ten years in our streets of heaviest traffic with a small amount of intelligent maintenance. There have been several charges made against wood pavements, which are mentioned here, not as a matter of information, viz., that they soon become full of holes, are impossible to clean, are difficult to replace when the street is opened, and that by their rotting the health of the community is endangered, to which may be added that for only a short time do they present any barrier to the saturation of the soil by surface water. The general practice, as far as observed by the writer, in this country has been to Xd^-^ green or wet pine blocks, more or less thoroughly dipped in coal tar, on a bed of sand, not always thoroughly rammed, with or without the interposition of a tarred pine board, with transverse joints from one to one and one-half inches wide filled with gravel and coal CONSTRUCTION AND MAINTENANCE OF ROADS. 87 tar, which was theoretically thoroughly compacted. Omitting those which, without the slight pretense of a i-inch board for foundation, speedily become a wood Macadam, the fifst failure was from the blocks rotting on the bottom in patches, so that the surface would first be found to be sheared down by a heavy load ; and on taking out the blocks they would be found sound on their tops, where the gravel had been driven into them by the traffic, and also a sound film of about the thickness that tar could be expected to penetrate a wet block, the inside being rotten. In other cases, however, when the layer of sand was too thin, the mud worked up through both boards and blocks, reducing everything to about the state of those having no boards under them. A layer of concrete, covered with Trinidad bitumen, will effectually stop the mud from coming up, and any percolation of the surface water into the soil through the pavement ; the narrow joints, by preventing the edges of the blocks burring over, will both tend to keep the surface smooth, lessening the shocks of the wheels, and greatly facilitate all the operations of cleansing. Creosoting, by the preservative and antiseptic properties of the dead oils used in that process, will probably keep the timber from decay, so that nothing but abrasion need be feared, and the sanitary objections to decaying wood will be removed. The following note of some experiments by E. R. Andrews (pub- lished in " Engineering News ") shows the efficacy of creosoting for pro- tecting wood from moisture. The following are the results of some careful experiments with differ- ent varieties of wood, half of the specimens being simply dried and the others creosoted, to ascertain to what extent wood is rendered water-proof by creosotmg. The specimens were soaked durmg two days m water, be- ing carefully weighed before and after soaking : Percentage of watei' absorbed. Spruce, creosoted 0236 0306 " dried only 1764 " Burnettized 2500 Hard pine, creosoted 0000 " dried onl}' 1 6oO Oak, creosoted 0625 '• dried only 2000 White birch, creosoted 1240 " dried only 4300 Cottonwood, creosoted 3470 " dried only 7140 Black gum, creosoted 1250 " dried only 1 .0000 Sesquoia Gigantea (great tree of California), creosoted 0000 '■ " " dried only 4722 In the rooms of this Society are creosoted fir ties from England that have been in the track for 20 years, and apparently justify the assertion of the engineer sending them, that they are good for 10 years more. 88 CONSTRUCTION AND MAINTENANCE OF ROADS. The following extract, from the " Railroad Gazette," is also corrob- orative : The German Railroad Union some time ago made inquiries as to the extent to which processes for preserving ties were employed, and what the results were. It appears from statistics of German railroads which have used treated ties more or less since 1840, and therefore have had time to test thorough- ly the life of the ties, that the average life of ties not treated, and of those treated with chloride of zinc or creosote has been : Not treated. Treated. Oak ties 13.6 years. 19.5 years. Firties .' 7.2 •' ' 14 to 16 Pine ties 5.0 " 8 to 10 " Beech ties 3.0 " 15 to 18 " The average life of 831,341 pine ties treated in various ways on thirteen German roads was 14 years. It follows from this that there is an increase in the life of ties treated with chloride of zinc or creosote, amounting to about 40 per cent, for oak, 100 to 130 per cent, for fir, 60 to 100 per cent, for pine, and 400 to 500 per cent, for beech. It thus appears that there is a great deal gained with any kind of wood, but most with some of those usually not considered good for ties, fir and beech being made almost as durable as oak. Bischoff says that it is of little advantage to secure the ties from decay for longer periods than above stated, as the ties usually become worn out or crushed by that time, even if not decayed. Commenting on these facts, Bischoff says that it is now generally ad- mitted that the choice lies between creosote and chloride of zinc ; that creosote is the best antiseptic material, but also that it is the dearest. There can be but little doubt that the antiseptic properties of the creosoting process are of more value than the increased life it would give lo the blocks. On account of the absence of proper stone and the cheapness of wood in large areas of our country, the small first cost of wood pavements seems to make it worth while to give them an intelligent trial. The thoroughness with which wood pavements can be cleansed de- pends on the size of the joints and the firmness of their filling. The practice in London, when the mud is at all sticky and not so thick as to require scraping, is to water and then sweep with a revolving broom, the thoroughness of the cleansing being almost directly as the amount of water. In hot w^eather a disinfectant is sometimes applied after sweep- ing. ASPHALTE AND BiTUMEN. Dictionary and encyclopedia makers, as well as chemists, seem to use these terms interchangeably. M. Leon Mab, in his " Guide Pratique pour La Fabrication et L' Application de L' Aspkalte et des BitumeSy* CONSTRUCTION AND MAINTENANCE OF ROADS. 89 after speaking of the lack of definition in the two terms as generally used, gives the following, viz. : '' Asphalte, Bituminous Limestone." " Bitiunen, The black and viscid substance which we find disseminated in the pores of bituminous limestone and in the interstices of the molasses of Seyssel or the sands of Auvergne." '' Asphaltic Mastic, Bituminous limestone transformed by dressing {cuissoti) and by the addition of a small quantity of bitumen." He adds : " We employ these definitions throughout this work, and give to them the senses which we have just indicated, and I hope strong- ly that they will be adopted for use, for they seem to be the most reason- able." It is believed his definitions have been generally accepted by European technical writers and in specifications relating to the use of these mate- rials,* and the writer in this paper will use them as above defined, except- ing that the bitumens from Trinidad and Cuba will be included with those mentioned by M Malo. In view of the practice in this country two other definitions seem neces- sary, viz.: Bituminous mastics, mixtures of bitumen, either having an earthy gangite, like those of Trinidad and Cuba, or purer ones, like Graharaite and Albertite, with limestone or other substances not naturally impreg- nated, which add to its resistance to wear, and — Tar Mastic, a mixture in which the bitumen is replaced by (usually) gas tar. M. Malo further characterizes asphalte as a carbonate of lime perfectly pure (excepting, sometimes, a trace of silica), naturally impregnated with bitumen. Its characteristic color is that of chocolate — which it also resem- bles in fracture — mean specific gra\ity 2.235. It is quite hard when cold, and falls to pieces at a heat of about 122 deg.-i4o deg. F. At an interme- diate temperature it flattens under the blows of a hammer ; its structure vanes with its locality, but in general should be fine-grained and homoge- neous, without particles of unimpregnated stone. In the poorer qualities the impregnation, though regular, does not ex- ceed 6 per cent., or the bitumen is injected into minute cracks, showing under the microscope that the impregnation is not molecular, or the rock contains clay, or, as in the case of Lobsan, the bitumen contains light oils which injure the consistence of the mastic, in which case the light oils are driven off by heat, the remainder being used. Generally, we may say that the more uniform and microscopic the impregnation of the lime is, and freer from extraneous matters, the better it is. *In Paris, the asphalted sidewalks are universally spoken of as bitumen, in distinction from ■wheel ways, which are called asphalte. 90 CONSTRUCTION AND MAINTENANCE OF ROADS. Neglecting the Tubal Cain stage of its history, asphalle was first ap- plied to sidewalks and wheelways as a mastic, but in that state was not sufficiently resistant for streets of much traffic. It was seen, however, that in summer the pieces of rock that fell from the carts between the mine and the mastic works at Seyssel compressed under the wheels. In 1849, a Swiss Engmeer, M. Merian, put this lesson to profit, by construct- ing a Macadam road of asphalte, which was compacted with a roller. In spite of the instability of its foundation and the irregularity of its mainte- nance, this road is still in very good order. (Malo, p. 108.) Compressed Asphalte. The first compressed asphalte was laid in Paris by M. Vaudry in 1854, though it was not till 1858 that it was laid on a large scale; the area covered in 1878 by pavements and cross-walks was 324,654 square yards, or nearly 14 miles of a street with a 40-foot wheelway. The earlier prac- tice was to " decrepitate " the rock (broken to about the proper size for Macadam) by heating it to about 140 degs. F. in sha low iron pans. Skill was necessary in this operation, as the rock was liable to be burned, /. e., have too m_uch of the bitumen driven off, or to have too little, and some- times both results were reached in the same batch. The walks in Union Square, N. Y., are an example ot the ill effects of unskillful decrepitation. The rock was also broken up by the direct action of steam, but it was impossible to secure a product of uniform fineness, and difficult to remove all the moisture. After experiments with various machines, a Blake crusher is first used, the pieces are then passed through a Carr's disinte- grator, after w^hich the powdered rock is heated in revolving cylinders to from 212 degs. to 284 degs. F. (depending partly on the distance it has to be carried), and transported to the place where it is to be laid, usually in covered sheet-iron wagons. The permanence of this pavement depends primarily on the stability of its foundation, which is usually of concrete (though old asphalte is sometimes used) 6 inches thick ; on this, when it is thoroughly dried, the heated powder is spread, by means of rakes, to such thickness that when compressed it shall be from 1% to 2% inches thick — depending on the probable amount of traffic. The compression, which is termed pilon- nage, is effected by the aid of the tools figured. The fouloir is first used along the junction of the asphalte with either the curb-stone or the paved gutters, while the rest of the surface is compacted by the pilon, beginning with light blows and ending with vigorous ones. All these tools are heated nearly red hot, as the powder sticks to them when they are cold. After the surface has been thoroughly compacted it is tested with a straight-edge, and then rubbed with the lissoir, also heated, giving a glaze to the surface, after which it is dusted over with cement and allowed to cool thoroughly before the traffic is turned on it. CONSTRUCTION AND MAINTENANCE OF ROADS. 91 Efforts have been made to secure a more regular surface than is prac- ticable by pilonnage and at less expense by rolling, but it was difficult to so heat the rollers that the powder would not adhere, and the pavement was liable to tear as it was about finished. The powder retains heat for some time, and the work goes on in a continuous sheet for the day, a gang of ten or twelve men being able to complete about 600 square yards per day. In the morning the uncom- pressed powder at the edge of the work of the day before is swept away, and hot powder put in its place, which in turn is removed after having heated the old work ; the spreading and pilonnage then goes oaas before, leaving small or no trace of the junction. Great care should be taken that the concrete foundation is thoroughly dry, otherwise the hot powder evolves steam, which permeates the powder Foulolr Pii°^- and leaves the compressed mass in nodules called almonds. These do not show during pilonnage, but are developed by the traffic, when the place is cut out and refilled. A very slight defect seems capable of starling a hole in compressed asphalte, and for the first two weeks it is under traffic it should be watched closely and repaired promptly. The defects caused by deficient aggregation of the molecules show themselves more readily than those caused by steam. Overheating, which renders the asphalte as inert as sand, is one cause of deficient aggregation, and laying the powder too cold IS another. When the asphalte is too rich in bitumen or the bitumen is too oily, the compressed asphalte forms waves under the traffic, sometimes longi- tudinal and at others transverse. So far but few asphaltes have been found that are available for com- pressed pavements. The Val de Travers (from Neuchatel) was first used. 92 CONSTRUCTION AND MAINTENANCE OF ROADS. . but in 1867 Seyssel (Pyrimont) was used with success in the Rue de Richelieu, and both have since been used by the General Asphalte Com- pany of Paris, which, until January, 1878, laid and maintained the asphalte roads in that city. The Val de Travers asphalte is of the two more reg- ular in its grain and impregnation, and richer in bit«amen, having 9 to 13 per cent. Seyssel is not so regular in its grain and impregnation, and contains from 7j^ to 10 per cent, of bitumen. The base of both is equally pure carbonate of lime, containing about 2 per cent, as a maximum of silica. Of the two, M. Ernest Chabrier, for a long time manager of the Paris Company, in his paper read before the Institute of Civil Engineers,, says : " No engineer could conscientiously say that the Val de Travers is better than the Seyssel asphalte. The former may be safer in the execu- tion of a work not subjected to supervision ; the latter offers greater guar- antees of good execution, because more care is required in the work." It was also held that, for compression at least, the two should not be mixed, and that only pure limestone, impregnated with from 8 to 12 per cent, of bitumen, was available for compression ; but within the last two or three years the Limmer & Vorwohle Asphalte Company of London found their mastic pavement breaking up and employed the .Sicihan arphalte (which is certified by W. J. Fewtrell, F. R. S., to contain as high as 30 per cent, of bitumen) in compressed pavements and sidewalks. Aldgate and Newgate streets having been laid with this asphalte are apparently wearing well. And in Paris, Paul Crochet, who has the contract for new work and maintenance for five years from 1878 (see Appendix, No. 4) has used, so far, a mixture of Lobsan and Seyssel Forens-Nord. M. Malo says of Lobsan : " It contains within its bitumen an oily substance which renders it too soft and injurious to the consist- ence of asphaltic mastic ; we free it from this oil by distillation, after ^ which it is in a proper state to be used." The Seyssel Forens is a heavy limestone, very poor in bitumen. As after a careful i»xVestigation the engineers of the Ponts et Chaussees have allowed it to be used in Paris- it seems that, theoretically, at least, a mixture of two dissimilar asphaltes is not disadvantageous, nor is the use of an asphalte that contains a hydro- carbon of the more volatile series ; also that, as in the case of the Sicilian,, an asphalte containing more than twice as much bitumen as was formerly thought the safe maximum can be successfully laid under exceptionally heavy traffic. There was an unwillingness on the part of the manager of the Limmer & Vorwohle Company to explain the manner in which he handled his material, but it is probable that it was skillfully roasted so as to drive off the excess of bitumen as his compressed roadways showed less tendency to roll in hot weather than those laid from Val de Travers rock. By the kindness of Count Kielmansegge, one of the directors of the CONSTRUCTION AND MAINTENANCE OF ROADS, 93 Neuchatel Company, I am able to give the following analyses of Val de Travers asphalte. These two sets of analyses by Charles Heisch, F. C. S., were made in consequence of complaints by their customers that the rock was becoming too rich in bitumen : September, 1876. 5 samples. 9.46 9.48 11.98 90.52 88.02 11.96 88.04 10.06 Carbonate of lime 90.54 89.94 Loss at 212° 100.00 1.46 100.00 100.00 1.42 3.04 . 3 samples. 10.2 100.00 3.22 11.5 88.5 100.0 2.6 100.00 1.92 Bitumen July, 1877 12.32 Carbonate of lime 89.8 100.0 2.46 t7.68 Loss at 212° 100.00 3.2 The loss was moisture and light oils. A small amount of silica was estimated with the lime. Mr. J. Knight, Secretary Society Francais des Asphaltes, gave me the following analyses made by Steen, of Copenhagen : rorcrnnir .0 no J Soluble in ether 9.62 a. oo.i P jr^^r.. jUigamc 1^-""| Insoluble in ether.. . . 2.35 Seyssel Pyrxmont ^ 33^,, j Soluble in acid 86.45 » "'( Insoluble in acid 1.55 'organic g.Ool?"^'^?'^^.^*^!!; ^ -f^ a«™=«i rS', Fig. 2, which works the right and left hand screws, jK R, throwing the axes of the rollers into radial positions; the other, or driving end of each axle, is stationary, with a spherical bearing — Figs. 1 and 2. THE LINDELOF ROLLER. This roller has an upright boiler, and two vertical cylinders that actuate a beveled gear which works into a gear bolted on to the driving wheel, the tread of which is a 1-inch plate of wrought iron ; the driving roller bears two-thiids of the weight of the machine. Both 10 and 15-ton roller* THE LINDELOF STEAM ROAD ROLLER. are built ; for the 10 ton, of 2,000 pounds each, the driving roller is 6 feet and the steering roller 5- feet long, giving a weight on the driving roller per inch run of 185 pounds. THE ATELING AND PORTER ROLLER. This roller, which is extensively used in this country, has been improved in several par- ticulars, and is believed to be the only roller now in the market that is run and fired by one man. As now manufactured the outside wheels are the driving wheels, the steering wheels covei-ing the space between them. The boiler is horizontal and multitubular ; the single steam jacketed cylinder is on top of the boiler, and runs a fly-wheel which by the aid of gearing drives the roller at a speed of about 2 miles per hour. The driving wheels have holes in their treads in which spikes may be placed for tearing up the road bed before remetalling, and the fly-wheel makes the roller available as a stationary engine to run a stone breaker. Four sizes are manufactured, viz., 8, 10, 15 and 20 tons in weight. Two-thirds of the weight is carried on the driving wheels, which have a width of 2 feet 2 inches for the 20-ton roller, giving CONSTRUCTION AND MAINTENANCE OF ROADS, 105 io6 CONSTRUCTION AND MAINTENANCE OF ROADS, a weight per inch run of 574 pounds ; the width of driving wheels on the 15-ton roller, is 1 foot 10 inches, giving a weight per inch of 509 pounds. The roller is fitted with a friction brake. THE BOSS KOLLEK. This machine is a combined road roller and rammer. Only one size is built, weighing 44,000 pounds. The boiler is vertical and the rams, any or all of which can be used or not, are actuated by cams. The length of the driving roller is 6 feet in all, vdth a space in the middle of 8 inches for the driying chain. The steering roller is 30 inches long. Four-fifths of the entire weight is carried by the driving wheel, giving a compressive force per inch run of 550 pounds. It is claimed that the traction is sufficient to allow it to mount grades of 20 feet per 100. Maximum speed, 5 miles per hour. The rams, five in number, are said to give an effective blow of 7,000 pounds each ; they are of .no use in compressing and puddling trap, but are efficient with limestone, and must be efficacious CONSTRUCTION AND MAINTENANCE OF ROADS. 107 for rubble foundations. The frame is utilized as a water tank, and the driving roller can be heated by steam for rolling mastics, &c. APPENDIX No. 4. A part of the Contract for the, Construction and Maintenance of the Streets and Sidewalks of the City of Jassy. Between M. Nicholas Gane, Mayor of Jassy, and Mr. W. O. Callender, of London. Article 1. The contract has for its objects : (a.) The construction of a system of streets with gutters and a system of side n^alks with curbs. (6.) The maintenance of the streets and sidewalks constructed under this contract. Art. 2. The construction consists of the following items of work : (a.) The construction of 47,853.8 square yards of streets, covered with compressed asphalte. (&.) The construction of 179,384.3 square yards of sidewalks, covered with asphaltic mastic. (g.) The construction of 17,038.4 square yards of roadway, paved with Macadam made from stone taken from streets now paved. (h.) The construction of 49,210 lin, feet of granite curbing for bordering the asphaltic mastic sidewalks on streets covered with compressed asphalte. Art. 3. The time fixed for the completion of this contract is five years, to begin with July 1st, 1873, and to end on March 31st. 1878. Art. 5. The labor of maintenance will consist in maintaining the streets in a constant good ■condition. On all the streets and sidewalks constructed by him, the contractor will repair, with his own laborers and his owu material, all degradations as soon as they appear, and will replace, the material lost. Art. C\ The length of the contract for maintenance is fixed at 15 years, to begin on May 1st, 18S0, and to end on April SOth, 1895. Art. 10. The transverse inclination of the asphalte sidewalks will be 2 per cent. Art. 11. The curbs of sidewalks of asphalte, on asphalted streets, will be of granite; those of sidewalks c-f asphalte, on streets paved with blocks or cobble stones, will be of sandstone, and the curbs of Macadam steeets, when they protect sidewalks of the same material, will be of stone cut from the old flagstones of the present sidewalks. The curbstones will be of the following dimensions: The faces parallel to the surface of the sidewalks will be 5.5 inches in width, of which 0.9 inch of the upper face will be eventually covered with asphalte. They will have a height of 11.9 inches, of which 6 inches will be under ground and the remainder above the gutter ; their length will not be less than 15| inches. The form of the curb will be that of a parallelopipedon, having next the sidewalk a rebate of 0.9 inch in width and a height equal to the thickness of the bed of asphalte. Art. 14. The gutters of asphalted streets shall have, according to the locality, a maximum ■width of 3.3 feet ; they shall be constructed of new cobble stones, well culled, or of new sand- stone blocks. At the edge of the asphalte there will always be laid a range of granite blocks 10,6 inches in length, 5.3 inches in width and 9 inches in depth. Art. 15. The sandstone blocks for the gutters will be dressed to regular cubes in form, of 9 inches on each side. Art. 16. The asphaltic rock, which must be natural and not artificial, must be from the best asphaltic quarries known: Limmer, in Hanover, Seyssel, io France, and Val-de-Travers, in SwJtzer' lard. The asphaltic mastic to be used must satisfy the following conditions : (a.) It must contain 12 parts of bitumen to 88 parts of asphaltic rock. (6.) The asphaltic rock itself must contain at least 7^ per cent, of bitumen, and at the most 93 per cent, of pure carbonate of lime. (c.) Kocks which contain, even in small proportions, quartz, sulphates, iron pyrites or alumi- num must be rejected for the composition of mastic. Art. 17. The bitumen used for mastic must be natural, not artificial, from the bitumen lakes of the Island of Trinidad, or fiom the asi)haltic rocks of Seyssel, if it is proved to be equal in quality to the Trinidad bitumen : it must be free from water ; its specific gravity must be from 1.1 to 1.5. Dipped in water at the freezing point, it must not lose its ductility ; its surface must io8 CONSTRUCTION AND MAINTENANCE OF ROADS. present no cracks or streaks. The surface of a fracture must be black and brilliant. It must be perfectly soluble in petroleum oil or the spirits of turpentine, and the solution when passed through a filter must leave no residue. (?) Art. 18. The quarry whence comes the bituminous rock, the mastic and the bitumen, must be certified by authentic certificates to be of even fabric and its products of the first quality. Each block of mastic must bear the trade mark of the quarry. Art. 19. The contractor is forbidden to have in his storehouses any asphaltic rock or mastic which do not comply with the conditions above stated and not In conformity with the samples deposited with the Mayor on the day of the signing of this contract ; he must neither use nor have in his storehouses any bituminous or resinous oils other than those specified in Article 17. All other material, resinous, bituminous or oleaginous and all other mastic than that like the samples deposited with the Mayor that may be found in the storehouses of the contractor will, on the first offense be confiscated, and a fine of 1,000 francs be imposed; in case of a repetition of the offense, confiscation and a fine of 5,000 francs; aiid should it occur a third time, beside the confiscation, the contract will be relet at the expense of the contractor's surety. Art. 20. The gravel employed in mixing the mastic must be taken from the beds of streams ; it must be thoroughly cleansed of all foreign matter, well washed, free from argillaceous matter,, and must be passed through a screen, the holes of which do not exceed 0.2 inch. Art. 21. The sand for making the mortar for beton and for forming the bed for asphalte, even that employed for bedding the street pavements, the gutters or curbs, shall be sharp, hard to the touch, and will be procured from the best open or working pits, or from the bed of running water. Art. 22, The cement will be the best from the best known quarries, such as Stefanesti or Eodeni. Art. 23. The stone used in mixing the beton will be broken stone from the quarries of Paun or Barnova. Each piece must pass through a ring of 2.4 inches diameter ; it shall be free from all foreign matter and well washed. Art. 24. The granite shall have the following qualities : (a.) It will be obtained from the hardest seams of the quarries ; it shall be homogeneous sonorous to the blow of a hammer, without flaws or fractures and free from foreign matter, (&.) It shall have a specific gravity of 2.65. (c.) After an immersion of 24 hours in water, it must not absorb more than ^Jjj of its volume.. (d.) When struck a hard blow, it must break in large fragments without leaving any detritus.. Art. 25. The sandstone shall be provided from the hardest beds of the quarries in Eoumania. The qualities of the sandstone shall be as follows: (a.) Under the blow of a hammer the sound of the stone must be limpid and pure ; a dull sound would indicate interior fissures, and would be sufficient to reject it, (&.) The specific gravity shall be 2.5. (c.) After an immersion of 24 hours in water, it should not absorb more than ^^^ ot its volume. Art. 26. The limestone for the beton shall be of the hardest quality, chosen from the hardest beds. Art. 27. The mortar for the beton of the sidewalks shall be composed of two parts of sand to one part of cement in volume. It shall all be mixed and wet with only as much water as may be absolutely necessary. Mortar which may set before being put in place will be rejected. The composition of the mortar for the beton which is to be used on the streets remains to be described hereafter, as also the compressed asphalte. Art, 28. The beton will be composed of three parts of broken stone to two parts of mortar. The beton which is not used after it is prepared will not be accepted. The streets which are to be covered with compressed asphalte shall be constructed in the following manner : (a.) The levels will be corrected, the ground shall be shaped to the form of the transverse pro- file fixed by the city, and will be sprinkled and rolled until it pres«»nts a smooth, hard surface, (&,) The curbstones shall then be set, care being taken to cut the joints on the ends as well as on the front edge, (c.) The part corresponding to the gutters will then be made of a bed of sand 2.4 inches in depth, in which will be laid the stones which form the gutters ; the sides of the gutters next to the CONSTRUCTION AND MAINTENANCE OF ROADS. 109 "bed of asphalte will in every case have a range of granite blocks. The remainder of the width of the gutters shall be paved ^^^th cobble stones, well assorted, in such a manner that the stones will all be of the same size, or with new sandstone blocks, agreeably to the city authorities. The gutters thus laid shall be well rammed wth a rammer, and over all shall be spread a layer of sand 0.4 inch deep. (c? .) That portion of the street which is to be covered with asphalte, will receive a bed of heton, the depth of which, after pilonnage, shall not be less than 6 inches. Upon the beton shall be spread a layer of brick broken to 0.4 inch in size. (e.) On this shall be laid the compressed asphalte, when the foundation shall have reached the desired consistency and become well dried. (/.) The asphalte will be laid according to the methods usually adopted on works of a similar nature ; the method of doing this remains to be discussed at a future day by the city and the con- tractor. Art. 33. The surface of the sidewalks shall be done over when needed, sprinkled and rolled ; over this shall be laid a bed of beton which after compression shall not have a less thickness than 3 inches. On this shall be spread the mastic to a depth of 0.8 inch. This mastic shall be com- posed of asphaltic mastic, gravel and bitumen in the following proportions : Asphaltic mastic 100 parts, gravel 60 to 72 parts, and bitumen 6 to 10 parts. The mastic and bitumen shall be melted in a portable kettle, so that they may be carried to the spot where they are to be used. The mas- tic shall be broken into small pieces, and shall not be poured until it is entirely melted. Durmg the melting the mastic shall be kept stirred, so that a thorough mixture may be insured and the mastic not allowed to burn. The mastic thus prepared shall be run over the beton in such a man- ner as to spread evenly over it. Before the complete solidification of the mastic which foi-ms the surface, sand will be spread over it and fixed by light ramming. At the junction between a cold and a hot bed, the edge of the cold one shall be reheated by spreading over it a coating of melted bitumen that wll then be removed and the final bed laid. Akt. &4. The tempering of the mastic should be such that it will support, at a temperature of 77 Far., the point of a rectangular pyramid of a height equal to one side of the base, without a depression occurring greater than 0.2 inch under a pressure of 154 pounds continued for five minutes. Art. 35. The sidewalks at carriage doorways shall have a foundation of beton 4 inches in depth after ramming, and the bed of mastic will be 1.2 inches. Art. 37. The junction of the mastic with the walls of the buildings bordering the streets will be made by means of a skirting, that is to say, the plaster will be scraped from the walls of these houses to a height of 2 inches above the level of the sidewalks, and the asphalte will be plastered on the bricks to the thickness of the mortar. The junction of the stratum of mastic with the posts, curbs, hydrants, and other objects of various natures will be made by heating these objects by a coating of melted asphalte that will be then removed and the final bed laid. Art. 42. The blocks and the cobble stones that the city authorities may declare unfit for using -again \s\\\ be broken and used as Macadam on streets designated by the city ; they shall be con- structed as follows : (a.) The ground shall be well graded, giving it the form and inclination of similar streets. (6.) On the surface thus prepared there shall be laid first, gutters of cobble stones to a width of from 2.5 to 3,3 feet. These shall be laid as specified for streets paved with cobble stones. (c.) On that portion of the ground designed for the roadway there shall be spread a bed of broken stone of 6 to 8 inches, reducing, after wetting and ramming, to 4 to 6 inches in depth. id.) On this strata of stone there shall be spread a bed of sand, which shall be well wet and rolled, so as to obtain a smooth and uniform surface. Art. 49. * * * * From the provisional recepfion, the maintenance of the work completed wll be performed by the contractor till April 30th, 1880. Art. 50. All unexpected degradations, all badly executed work, not only during the progress of construction, but also during the years of maintenance, will be repaired by the contractor, what- ever may be the cause of the degradation, and with the least delay, without waiting to be notified no CONSTRUCTION AND MAINTENANCE OF ROADS. by the city, under penalty of a fine ot 50 francs for each diiy of delay after the three first days Avhlch follow that of the discovery of the degradation. Besides that penalty, if the contractor does not proceed immediately to the reparation of these unforeseen accidents, the city shall have the authority to put them in good repair in his place and at his expense, by deducting the cost from the estimate. Akt. 51. On April 1st, 1878, the city will make a new and minate inspection of all the work done during the five seasons. They will compare the state of the work done with that of each of the estimates made at the end of each season, and if it be found that the works are in compliance with this contract, and in good condition, they will finally accept them and make out a new esti- mate, of which a duly certified copy will be furnished the contractor. Art. 52. On May 1st, 1880, the contractor having satisfied the first part of the obligations de- volving upon him under this contract, binds himself under a new obligation to the city, that of maintaining for a period of fifteen years, from May 1st, 1880, to April 30th, 1895, the works exe- cuted, in consideration of a price agreed upon in advance. Art. 53. The maintenance consists in repairs, renewals and furnishing materials necessary to the sidewalks, curbs, gutters, etc. ; in doing all kinds of work and furnishing materials necessary to at all times maintain the surface of the streets and sidewalks paved by the contractor, in a per- fect state of uniformity. The uniformity of the surface of the streets and sidewalks shall be determined by the use of a templet of iron formed to the normal curve adopted for the surface of the streets and sidewalks. This templet, applied to a street or sidewalk, must not present at any point a swell or depression greater than 0.4 inch. The surface of the streets and sidewalks shall not show any cracks. The connections witk the curbs must be perfect. Art. 54. "Whenever the curbs, the sidewalks, the roadways, the water ways — in a word. everything that goes to make a part of the street, becomes subject to a displacement or derange- ment from any cause whatever, the contractor will be obliged to repair them immediately, in con- formity to the preceding article. Exception is made, however, to all that applies to the construc- tion or repairs of water or gas mains, which will always be at the expense of the respective grantees. Art. 55. The contractor shall proceed at once, at his own cost, to repair any degradation whatever, without notification from the city. Whenever a notification from the city becomes necessary to warn him to proceed with the re_ paration, the contractor will be liable to a fine of ten francs, and he will be obliged to proceed with the reparation within 24 hours after the receipt of such notification. If, after that notice, the contractor fails to proceed with the repairs of the degradation indi- cated by the citj^, the latter shall proceed with the work ; it shall make the reparation, submit the contractor to a fine of fifty francs, and retain the cost of the reparation and fine from any sums that may accrue for the maintenance of the streets, and in case that should not be sufficient, from the sureties. In case of a repetition of this offense occurring during the cours% of a single year, the city, be- sides the right which it always reserves to make the reparation on the account of the contractor, in conformity with the preceding paragraph, will impose ou the contractor a fine of 1,000^ francs. Finally, on a third infraction in the course of the same year, the city has the right to make besides the reparations after the rules estabfished above, and of re-letting the work of maintenance to another at the cost of the contractor ; if this sale results in a loss to the city, it shall have the right to reimburse itself from the sureties. In case, on the contrary, it results In a profit, th& contractor shall have no right to demand it. Art. 59. The prices for the works executed in conformity to the requirements of this contract shall be : (a.) For compressed asphalte, $5.38 per square yard. (6.) For sidewalk asphalted, $2.81 per square yard. (c.) For roadway, with gutters, paved with sandstone blocks taken from streets now paved,. $1.94 per square yard, (d.) For roadway or gutters paved with new sandstone blocks furnished by the contractor^ $8.41 per square yard. CONSTRUCTION AND MAINTENANCE OF ROADS, iir (e.) Forroadwaj-, the gutters included, paved with cobble stones taken from streets now paved in that manner, also for gutters constructed with cobble stones on Macadamized streets, $1.02 per square yard, (f.) For roadway paved with cobble stones furnished by the contract ir, also for gutters paved in this manner on streets covered with compressed asphalte, $1.91 per square yard. (g.) For Macadam roadway, $1.45 per square yard. (h.) For granite curb to asphalted sidewalks, $0.95 per lineal foot. (i.) For sandstone curb to asphalted sidewalks, $0.67 per lineal foot. (fc.) For curb cut from the old sandstone s;abs or flags. $0.39 per lineal foot. (l,) For granite curb used in the edging for asphalte of streets, $0.81 per lineal foot. Art 57. The price for maintaining the roadway and sidewalks during 15 years from May 1st, ISSO, to April 80th, 1S95, shall be calculated from the total area constructed by the contractor, and shall be as follows : (a,) For maintaining compressed asphalte streets with granite curb, $0.09 per square yard per annum. (&.) For maintaining asphalte sidewalk, whatever the kind of curb, $0.04^ per square yard per annum. ic.) For maintaining roadwaj^ or gutter paved with old or new stone blocks, $0.29 per square yard per annum. {d.) For maintaining roadway or gutters paved with cobble stones, $0.09 per square yard per annum. (e.) For maintaining Macadam, including the sidewalks and curbs, $0,15 per square yard per annum. Art. 5S. Payment for work done will be made to the contractor in the following manner: One-quarter of the work done will be paid for in cash, the remainder in City bonds. The bonds will have 15 years to run ; they will bear interest at 6 per cent, per annum, pay- able semi-annually ; they will be deUvered to the contractor at par. Art. 67. The sums due for the maintenance of streets and sidewalks during the 15 years which follow the construction— from May 1st, 1880, to April 30th, 1S95 — will be paid by the City of Jassy, at the end of each month, after deducting all that the contractor owes to the City for repairs made in his name and at his expense, and fines. These payments will be made in gsA. arts. 69 to 71, inclusive, provide that the contractor shall place a guaranty of 100,000 fvimf?, in bonds of Eoumania, which may be replaced by bonds of the City. In addition 10 i)er cent, of contract price shall be retained, until the sum of 400,000 francs is reached, making a total guaranty of 500,000 francs. This guaranty shall be returned to him as follows: May 1st, 1878, 250,000 francs ; and at the end of the years ot maintenance. May 1st, 1895, 250,000 francs. Art. 72. Six months before the expiration of the fifteen years of maintenance, the City authorities will make a general .inspection of all the work done and maintained and make an estimate of it. Art. 73. If during this inspection the City discovers the necessity of any repairs, the con- tractor shall do the same at his own expense during the following six months, in such a manner that the streets maintained by him shall be turned over to the City in a good condition on the day the contractor completes his contract. Should the contractor refuse to make these repairs, the city shall proceed to do it at the ex- pense of his warranty. Art. 74. At the end of the 15 years of maintenance, if the streets are in a good condition, considering only the effects of the weather, but presenting no degradations, the final acceptance of the works will be made and the guaranty deposited by the contractor returned to him. The coupons of bonds deposited as guaranties are the property of the contractor, who will have the right to collect the sums corresponding to each. The contractor shall also have the right to replace the bonds deposited by him as guaranty whenever they may become extinguished through the process of drawing lots. Art. 89. The system allowed for the pavement of the carriage wi:ys is that of compressed asphalte. The manufacture of this compressed asphalte will not depart from the rules actually adopted by science and experience, the mode of execution of the compressed asphalte remains to be agreed upon hereafter between the City and the contractor. 112 CONSTRUCTION AND MAINTENANCE OF ROADS. APPENDIX No. 5. Abstract of Specifications and Schedule of prices for the construction and main- tenance of foot-paths and sidewalks, in asphaltic mastic, and the Places and roadways in compressed asphalte belonging to Municipal service of Paris, from January 1st, 1878, to December 3lst. 1882. Paul Crochet, Contractor. Article 1. The work has for its object— 1st. The maintenance and construction of foot paths and sidewalks in asphaltic mastic, situated in the pubhc ways. 2d. The maintenance and construction of compressed asphalte pavements. 3d. The new works ; these works will com- prise all the pavements in bitumen and asphalte. Art. 4.— The present letting is made on a scale of prices, and the amount of the work is completely undefined, so that the contractor cannot make any demand on account of any changes that the expenditure may be subject to. Art. 6. When the adjoining proprietors or other parties in interest have to bear the cost of the works detailed above, or to contribute in any proportion, the contractor will be held to execute the work at the same price as that done at the cost of the City of Paris, and conformably to the ■orders of the Engineers. Art. 7. Foot pavements shall have the widths determined by the administration, they shall be composed of pavement in mastic supported on the side of a public road by a curb the height of which shall commonly be of 6^ to 4 inches. Art. 9. The ordinary curbs in gi-anite shall be llf inches wide on top with a total fall across off inch ; 13 inches wide at the base, which shall be horizontal ; llf inches high on the front face, which shall have a batter of 1^ inches. Art. 16. The mastic pavements will be formed of a layer of pure asphaltic mastic at least x% inch thick, resting on a bed of hydraulic concrete 4 inches thick which comprises a covering of hydraulic mortar at least f inch thick. Art. 17. The compressed asphalte pavements will consist of an upper layer of compressed asphalte 1^ to 2i inches thick, resting on a foundation of hydraulic lime or cement, concrete 4 to 6 inches thick covered as above with mortar or upon an old Macadam roadway picked over and covered with a thin coat of hydraulic mortar. Art. 21. The asphaltic mastic employed either for new or repairing old paving shall be com- posed of naturally impregnated rock with natural bitumen of good quality, coming exclusively -from mineral rocks. The fictitious bitumens extracted by the purification of the heavy oils of schists, the distilla- tion of coal, those so-called fatty bitumens and all other analogous products shall be rigorously proscribed. The rock employed after being reduced to powder will be melted with a sufficient quantity of purified natural bitumen to form a mastic which, when cold, presents a homologous mass slightly elastic, and which does not soften under a hot sun. This mastic shall be moulded into blocks. There may also be used blocks of bituminous mastic with a base of slates manufactured by the process of M. Sebille. Art. 22. The contractor shall be bound to employ under the orders of the Engineer upon each public way the bituminous mastic above described. The mastic shall be formed of a mixture of natural bitumen, in the proportion of one-twelfth of its weight at most, and the calcareous asphalte rocks of Seyssel, Seyssel-Forens, Pyrimont or Volants, of Val de Travers or Lobsan, or others deemed equivalents by the Engineers. The mastic, having a bas« of slate of M. Sebille, will be formed of a mixture of bitumen described in Art. 23, following, and of powdered red or blue slate of Ardennes, powdered chalk of Mendon or of Nanterre and of silica from the basin of Paris, in the following proportions, by weight : Eefined mineral bitumen 30 Ground slate 35 Powdered chalk 10 Silica, ground and sifted -, 25 100 CONSTRUCTION AND MAINTENANCE OF ROADS. 113 Art. 23. Ihe bitumen shall come as much as possible from the washings of bituminous sandstone or the asphaltic rock of Maestu, and in their default, from the dry pitch of Trinidad, perfectly pu'ified. It ought to be viscid at the ordinary temperature ; never brittle or liquid ; drawn into threads it should lengthen and only break in very fine points. Art. 24. The rock employed should be calcareou!», soft, with fine grain, texture fairly com- pact, regularly impregnated with bitumen so as not to show black and white spots ; it should be of a brown color ; heated to 122 to 140° F. it should soften and break on being torn. Care must be aken for the areas in asphalte to choose only such pieces as are of the most even grain and richest impregnation. The rock of Lobsan, however, should not be employed alone in the asphalte roadways, it ought to be mixed with other rocks less fat in proportions, which will be de- termined by the Engineers according to the composition of the other rocks. It should contain at least 7 per cent, of bitumen, and at the most 93 per cent, of lime; its change into mastic must not require more than 9 per cent, of bitumen. Art. 25. The materials entering into the composition of the pavements are the mastics described in Art. 22, pure gravel grit and natural bitumen to assist the melting. These materials ought to be generally employed in the following proportions, by weight: ( Asphaltic mastic 100 Foot pavements with a base of asphalte. .K Bitumen 6 ( Grit 60 ( Asphaltic mastic 100 Foot pavements with a base of slate •< Bitumen T / Gravel 50 Art. 26. One month before the award of this contract the competitors must deposit at the office of the works in Paris, samples of— 1st, A block of the mastic described above; 2d, Speci- mens of the asphaltic rocks and the natural bitumens they intend to use; 3d, A note indicating the elements of the composition of the mastics and proportions of the various rocks that they intend to employ in the composition of the asphaltic areas. The blocks and specimens of rocks and bitumen to have the trade-marks of the works from whence they came and the signatures of the competitors. The necessary certificates to compete for the contract will not be delivered till after the examination and acceptance by the Engineers of the specimens deposited. During all the term of this contract the contractor can only use materials exactly similar to the sjjecimens de- posited. Art. 27. Provides for continuous inspection of the contractor's works or the right to compel the contractor to manufacture the mastic in the depots belonging to the city. Art. 31. The lime employed is to be hydraulic lime in powder. It must be brought onto the works in sealed bags, marked wiih the name of the maker. Only the lime and cement designated in the specifications for the construction and repair of sewers will be allowed. A3T. 32. The broken flint must pass through a ring of 2^ inches and be at least |-inch thick. It must be free from earthy matters and washed clean. Art. 33. The sand shall be dredged from the Seine and well cleansed from all foreign matter; it shall be screened from all grains larger than | inch for the mortars, or ^% inch for grit for the mastic pavements; the grit for this last purpose shall be perfectly washed and dried before use. Art. 34. The mortar of hydraulic lime shall be composed of 5 parts of sand and 2 parts of lime, by volume, furnished in powdeu; the mixture shall be directly reduced to a paste by adding the quantity of water exacth' required to reduce it to the consistency of plastic clay. The cement mortar shall be composed of one part of hydraulic cement of Bourgogne or Port- land cement of Boulogne and 3 parts of sand; the sand and cement shall be thoroughly mixed before the addition of any water. All mortar which shall have set shall be rejected. Art. 35. The beton shall be composed, ordinarily, of two parts in volume of mortar and three of stone. The mixture, made either by the rake or cylinder, must be perfectly uniform. All beton not used at the time of making shall be rejected. Art, 86. The bed of beton for the foundation of the sidewalks shall be well rammed and com- pressed, and must at least commence to set and dry before receiving mastic or asphalte. The beton shall, In addition, be covered with a layer of mortar f inch thick. 114 CONSTRUCTION AND MAINTENANCE OF ROADS. The gravel for foundation shall pass in every direction through £ ring 2 inches in diameter. It must be perfectly compressed and sprinkled wlthlime grout. This foundation shall have com- menced to set before the application of the mastic, and shall be covered with a layer of mortar like the beton. Art. 39. The ground upon which the mastic pavement is to b-^ placed shall always be pre- viously rammed, watered, and crowned with care. When it is thus made solid the contractor shall spread over it the foundation layer, formed according to the orders of the Engineer, either a bed of beton or of sand covered by a Lyer of mortar, or a bed of sand impregnated with goudron 2f inches thick, or any other foundation prescribed by the Engineer. In all cases the pavement shall not be laid till the foundation has attained the firmness desired, and become quite dry. The contractor must conform to the following orders for the manufacture of the mastic to be used for pavements. The mastic shall be prepared and cast in one or more manufactories belonging to the con- tractor, and which shall always remain open to the inspection of the engineers and their agents. The contractor sha'.l, besides, establish in the manufacturing depots, both of asphalte and mastic, oflSces exclusively for the agents of the administration set apart for the inspection of the composition of these materials. These materials shall not be admitted into the works without a cai-ter's delivery note given by the inspector, setting forth that they have been manufactured in accordance with the specifications. There shall only be allowed in the works blocks of mastic conforming to the samples de- posited and accepted before the award, and bearing their trade-mark, or the old mastics from the walks and streets of Paris. All other bituminous matters, resinous or fatty, found in the works by the agents of the administiation will subject the contractor to a deduction of $100 for each time. To assure the execution of these conditions the contractor must not have in any manufactory, under the same penalty, any other blocks than those which should be prepared in his works, and the old mastics taken up. The use of the old mastic is authorized in the works of the city in the proportion of one-half with the new. The pieces of the old sidewalks having been perfectly cleaned with great care, and regenerated by the addition of new purified bitumen and a suflacient quantity of powdered asphalte to render the old mastic, when melted, of the aspect and consistence of the blocks in fusion. This mastic shall be melted in hermetically closed boilers, on wheels of a model approved by the administration, and arranged so that the material can be conveyed from the factory to the place to be used, ready to be employed. For melting, the mastic is broken into pieces 4 inches cube, then the bitumen is melted and the mastic added little by little. The grit must not be thrown into the boiler till the mastic is completely dissolved. During the whole time of the operation the matter must be stirred up almost constantly, so that the combination shall be well made and the mastic not burned. The mastic being well melted and perfectly homogeneous, it shall be run out in bands of about 5 feet wide, spread with a wooden float, and leveled with a strike, so as to present neither fissure nor joint. The mastic must be perfectly level, and match exactly with the curbs, &c., against which it is laid. For this purpose {he parts of the curbs, flags, Ac, which will be in con- tact with the bitumen shall be previously warmed and goudroned. Art. 40. Upon the soil, well shaped and rammed, shall be placed a bed of concrete, covered with a layer of mortar. The asphaltic rock, conforming to Article 24, broken down or decrepitated by heat, shall be raised to a uniform temperature of Irom 248° to 266° F., and carried to the place of employment in vehicles that will prevent as much as possible the loss of heat. It must be completely freed from the water it contains. The use of old compressed, taken from old roads, is authorized for mixture with new asphalte, in the proportion of one quarter of old compressed to three-quarters of new rock, provided that the old shall be cleansed with great care before grinding and mixing with the' new. Asphalte shall not be put on the concrete foundation until it is peerfectly set and dry. CONSTRUCTION AND MAINTENANCE OF ROADS. ii$ The powder shall be spread with a thickness about two-fifths inore than the finished thick- ness, leveled with great care, shall be rammed at first carefullj^ then gradually augmenting the force by means of cast-iron pilons, heated to the proper temperature in portable furnaces. In specially exceptional cases, the compression may also, wth the written permission of the Engineer be accompHshed by means of rollers. In every case, after the pilonnage is finished, the surface shall be smoothed by means of % heat-'d iron Uissoir). The road shall not be open to traflic until it is quite cool. Art. 41. The specifications referring to the construction of roads and footpaths are applicable to the maintenance of the same. The contractor will be entitled to the old material, and will make the repairs in new material or in the mixture specified in Articles 39 and 40. Art. 43. In conformity Avlth the contract price, stipulated hereafter, diminished by the rebate of the awarded contract, the contractor must make the necessary repairs to all asphaltic mastic footpaths and areas, furnishing the necessary labor and materials, so that they shall be kept in a proper state. He must each 3'ear of the duration of the contract completely relay, in new material, at least the fifteenth part of the surfaces of masr tic and compressed asphalte. The surlaces in mastic must be properly plane and regular, presenting neither hollows nor projections' of more than three-eighths of an inch in a circle whose radius is Z\ feet. These surfaces must be free from fissures. Art. 45. As the works in asphalte or mastic are received by the engineers thej' will pass into the charge of the contractor who will receive for the maintenance the price stipulated, commenc- ing from the 1st of January next following their acceptance, whatever may be the date of said acceptance. Art. 46., The contract prices diminished by the rebate of the award are applicable to the entire surface occupied by footpaths or compressed asphalte, whatever may be their condition. In the nine last months of thq year installments may be paid on the contract when the engi- neers recognize that the conditions have been loyally carried out. The accumulated sums of these installments must not exceed four-fifths of the amount of the sums which shall be due after the time has expired. The balance of the contract price of the year will be paid in the course of the first quarter of the following year. Art. 47. The repairs over trenches for sewers, water and gas-pipes, or other works, will be paid for once at the schedule price, but no demand for further payments on account of sinkings or other dilapidations will be entertained, and the surfaces on these trenches must be kept in the same good condition as the others. For the purpose of securing settlement, the contractor may- keep the trenches repaired with flint (Macadam) not longer than 15 diys. Art. 49. All damages in the bituminous surface, such as fissures or cracks of at least ^'g inch in width, or parting from the curbs y'g inch in width, any lifting up or breaking away of the mastic for at least j^'g in depth, depression in consequence of settlement of f inch at least in depth under the straight edge, 3J feet long, will subject the contractor to a deduction of 3 francs (58 cents) per day, when the repairs shall not have been done within 48 hours after notice given by the Engineer. Art. 51. During the continuance of frost, and during the first month after the commence- ment of the thaw, there shall be no repairs to the pavements maintained by the contractor, and the inspection for defects shall be suspended, but the contractor shall fill with sand and gravel any holes in these pavements within 24 hours after notification by the Engineer, under a penalty of 10 francs ($1.9;3) for each day they remain unfilled. He may be authorized, in exceptional cases, to fill the holes with broken flint or melted bitumen, but must replace the flint or bitumen with as-^halte as soon as the weather permits. It must be so arranged that the main repairs, intended; to re-establish the normal outline of the roadways, are effected from May Ist to November 1st. Art. 57. The contractor shall execute in private houses the junctions rendered necessary by changes in the public way, which will be paid for according to the price of his contract, subject to the rebate when the works are executed on account of the city. Art. 65. When a workman leaves one of the districts of the works under the Municipal ser- vice, he must have a certificate from the contractor showing the cause for which he left. This certificate shall be submitted at once to the Engineer, who shall be at liberty to refuse the right of employing the said workman, without the contractor deriving therefrom any excuse ii6 CONSTRUCTION AND MAINTENANCE OF ROADS. for not furnishing, when requisite, the number of -workmen required. In default of a certificate, the workman cannot be admitted, except on the written order of the Engineer. Note. — There are 75 articles in this contract, those not given referring to the setting of curbs, etc., transport of materials, and the relations between the Engineer and contractor. SCHEDULE OF THE PRICES FOR THE WORK SPECIFIED ABOVE. Note. —All the prices below comprise the incidental expenses and the profits of the contractor and are subject to the rebate of the award. (This contract is let in three lots, the rebates are 7j?, 20.2^, and 14$^, respectively.) Day Work.— The day of a workman, cart or machine shall be ten hours of efl'ective work in all seasons ; fractions more or less shall be counted by the hour, or ^^j of the day. The night hours shall be paid half as much more as those of the day, excepting watchmen. Night hours will be counted only from 7 p. m. to 5 a. m. in summer, and from 5 p. m. to 7 A. m, in winter. The summer period begins March 1st, and winter November 1st. 1. A day of a laborer , 9&i 2. " an ordinary mason 1.06 8. " an asphalte helper, or of a mason's or paver's helper 87 4. •' granite cutter 1.35 5. " sandstone cutters, pavers and asphalte workers 1.26^^ 6. " watchman ' 53 7. Night watchman 79 8. Day of one-horse wagon and driver. ., 2.70 9. •' two-horse " " 4.05 21. 1 cubic yard of stone broken for concrete 1.22 22. " ground hydraulic cement 513 23. " river sand 1.18 24. " pit sand 89 25. " river sand, washed and dried for mastic 1.48 27. 100 pounds of Roman cement 58 28. " Portland cement 67 29. " asphaltic rock 68 30. " mineral goudron, from Lobsang, Bastennes, or other recognized as equivalent to them, and purified Trinidad or Maestu . . 3.24 49. 1 cubic yard of mortar, composed of two parts of ground hydraulic lime and five parts of sand 3.10 50. 1 cubic yard of mortar, composed of one part of hydraulic cement uf Bourgoyne and three parts of .«and 5.02 51. 1 cubic yard of mortar, composed of one part of Portland cement and three parts of sand 6.42 52. 1 cubic yard of concrete, composed of three parts of broken stone and two parts of mortar ( J^To. 49) 8.03 63. 1 cubic yard of concrete, composed of three parts of stone and two parts of mortar (No. "50) 3.99 64. 1 cubic yard of concrete, with mortar (No . 51 ) • 4.65 55. 100 pounds of natural bituminous mastic in blocks, made from rock of Seyssel, or other equivalent, ready to be employed 1.02 6[). 100 pounds of compressed asphalte, taken from streets to be repaired, shall be taken by the contractor (without rebate) at 35 61. 1 square yard of old sidewalks in mastic shall be taken by the contractor, without retrard to its thickness and without rebate, at , 19 70. Taking up 1 square yard of compressed asphalte, piling the material included 014 71. Taking xap 1 square yard of mastic sidewalk, with piling the material 003 73. Cleaning and leveling an old Macadam road to secure a surface of mortar for com- pressed asphalte, per square yard 10 93. 1 square yard of new natural a«phaltic mastic, 0.6 inch thick 53 94. Greater or less value of each x^ of an inch in thickness 045 95. 1 square yard of sidewalk relaid in natural asphaltic mastic, 0.6 inch thick, the old material belonging to contractor 40 96. Greater or less value of each -^%^ inch in thickness 025 97. 1 square yard of pavement, 0.6 inch thick, composed of one-half new and one-half new and one-hnlf old mastic 50 98. 1 square yard of repairs of pavements composed as above 32 99. For each j§g in thickness, more or less 02 CONSTRUCTION AND MAINTENANCE OF ROADS. 117 102. 1 square yard of compressed asphalte, 1.6 inches thick, comprising regulating the surface of the ground, hut neither excavation, embankment nor foundation of con- cret-^ 173 103. For each i Jo in thickness, more or less 17 105. 1 square yard repairs of road 1.6 inches thick, the contractor retaining the old ma- tt-rial 1.04 106. For each ^%^ in thickness, more or less 17 lOS. 1 square yard of foundation for pavement in asphalte or mastic, comprising regulat- in'g aid ramming the roadbed, but not excavation. 109. 1 square yard concrete of hydraulic cement rammed to 4 inches] in thickness, com- prising a covering of mortar. No. 49, at least j J^ inch thick 34 110. 1 square yard concrete of cement. No. 53, rammed to 4 inches thick, comprising a covering of mortar, No. 50 46 111. 1 square yard concrete of cement, No. 54, rammed 4 inches thick, covered with mortar No. 51 54 112. 1 square yard on natural soil, with a bed of sand 0.8 inch thick . . 04 117. Kepairs in which all or a part of the old materials are used, will be paid for at three- quarters of the prices above mentioned. 207. 1 square yard of sidewalk, in natural mastic, half an inch thick, comprising a hydraulic hme concrete foundation, 4 inches thick after ramming, with regulating but not ex- cavatinar 93 208. Note. When the foundation is in cement concrete the price above will be increased hy the respective dillerences between each of the prices of Nos. 110 and 111, and that of 109. 209. 1 square yard of mastic like 207, on the natural ground, covered with a bed of sand 0.8 inch thick 63 210. 1 square yard of mastic Hke 207, on the natural ground, covered with hydraulic mor- tar 6a 211. Note. When the pavement is one-half new mastic with old material, the prices above will be dimished by 09 812. 1 square yard of compressed asphalte 1.6 inches thick, including a foundation of hy- draulic lime concrete, rammed 4 inches thick. Including dressing and ramming the soil but not excavation 2.07 213. 1 square yard of compressed, with concrete of cement No. 51 , 2.21 Additional price for work executed on embankments more than 1 yard high, or on trenches, whatever may be the thickness of the pavement or concrete. 215. 1 square yard of mastic 22 216. " " compressed 36 217. Maintenance of 1 square yard of sidewalk in asphaltic mastic, in conformity with these specifications, per annum ■ 05 218. The same for roads in compressed asphalte 19- 219. Additional price for maintaining cross-walks of compressed asphalte on Macadamized roads, and of gutters bordering them 10 248. For works not mentioned in the present schedule, che prices in the schedules now in force for maintenance of public ways or sewers and water service will be paid: which prices will be subject to the rebate of the present letting. DISCUSSION ON THE CONSTRUCTION AND MAINTENANCE OF ROADS. By Arthur Spielman and Charles B. Brush, George D. Ansley, A. B. Hill, Charles Douglas Fox, E. Lavoinne, E. B. Van Winkle, B. F. Morse, E. S. Chesbrough, E. R. An- drews, C. Shaler Smith, M. Merriwether, J.E. Hilgard, D. E. McComb, F. Rinecker, J. J. R. Croes, John Bogart, C. C. Martin and Edward P. North. A. Spielman and Charles B. Brush (Spielman & Brush). — Some of the views expressed in Mr. North's paper on "the construction and maintenance of roads," being at variance with the results of the ex- perience of our firm, in the building of 36,000 square yards of Telford roads in 1875 and 1876, and about 25,000 square yards in 1878 and 1879, part of this latter am'^unt being now in the course of construction, we herewith submit the principal facts in relation to these roads, and our conclusions therefrom. The roads are 80 feet wide between house lines, and are located in the northern part of Hudson County, New Jersey ; they are built exclusively of trap rock, obtained from and along the line of the road, the stone for the upper courses having been broken by a stone crusher erected on the road by the contractor, the average haul from the crusher not exceeding 2,000 feet. No binding except the screenings and detritus of the stone was al- lowed in the work, and in each case the foundation is of rubble, 8 inches deep, and the superstructure of broken stone, 4 inches thick, when com- pacted. The roads built under our direction in 1875-1876 may be divided into two classes : 1. Roads by the side of horse railroad tracks. 2. Roads free from horse railroad tracks. I20 CONSTRUCTION AND MAINTENANCE OF ROADS. In the first case the width of the roadway from curb to curb is 55 feet, which includes 18 feet of trap block pavehient for the tracks, and 5 feet for the gutter. In the second case the width between the curbs is 40 feet, including 5 feet of block pavement for the gutter. In both cases the 8-inch foundation was first carefully laid, and great care taken to allow for perfect sub-drainage. Cess-pools, filled in with broken stone, were built at intervals of about 200 feet on both sides of the road, which collect all the water that accumulates in the foundation of the pavement, and these cess-pools are drained by 6-inch stoneware pipes into adjoining receiving basins. A particular illustration of the importance of this sub-drainage came under our notice. In December, 1875, just after considerable of the foun- dation had been laid, legal difficulties arose, the work was suddenly stopped, and remained in this unfinished condition until the spring of i876» receiving in the meantime the wash from the adjoining hill-sides. When the work was recommenced the interstices between the foundation stones of the pavement in many places were filled in with earth. After unsuccess- fully attempting to remove this earth, the foundation at these points, as far as they could be ascertained, was taken up and relaid : but as soon as the superstructure of the road was completed we found that, in certain spots, it was always wet, and the surface of the road was continually broken. These spots invariably indicated the points where the foundation was clogged, and the difficulty was only effectually remedied by relaying the foundation, or by building blind drains which carry off the accumulat- ing water. On the top of the foundation thus prepared, 2-inch stone was then put on, sprinkled, ar.d rolled with a horse roller of 150 pounds per inch run. The one-inch stone and scfeenings were then spread, sprinkled, and rolled with a steam roller of about 400 pounds per inch run. After the rolhng was partially completed the passing traffic was allowed upon it, and any large stones that came to the surface, as well as all small stones that failed to bind, were raked off and sent back to the crusher to be re-broken for screenings. No water-worn or other rounded stones were allowed m the work. Advantage was taken of every rainfall to roll the surface of the road, because we found that it could be com- pacted much more thoroughly in wet than in dry weather. Where the pavement was laid in a soft substratum it required nearly double the amount of rolling sufficient for a solid foundation. The grades of these roads vary from 6>^ feet to 8 inches per 100 feet and the crowns vary from 1 2 inches to 8 inches. The roads have now been open for traffic about three years ; those along the railroad tracks are used by about 600 wagons per day, the CONSTRUCTION AND MAINTENANCE OF ROADS. 121 others by about 400 wagons per day. Fully one half of the traffic on both roads consists of heavy beer wagons from the adjoining breweries, stone trucks and ice carts, ranging in weight from 3 to 6 tons ; the balance of the traffic, of ordinary farm wagons, carriages, etc. No especial care has been taken of the roads, except to see that the gutters and culverts are kept clean. No ruts have ever appeared, and the surface is now smooth and in good condition. In hot weather the roads are somewhat dusty, and in long dry spells they will loosen and break up in spots, where disturbed by the corked shoes of horses drawing very heavy loads, but after the first rain the surface immediately rebinds and again becomes perfectly smooth. Wind and water are, perhaps, the two greatest enemies of Macadam roads ; the wind, by blowmg off the slight dust which naturally accumulates on the surface, removes from the road the cushion, which is not only a relief to the traveler, but which also preserves the metal of the road from a vast amount of wear and tear; the water, by flooding the road, has sometimes the same effect as the wind, and if by any means the surface of the road is exposed to a running stream the stones are sure to loosen. The only effectual remedy we found was to ra'se the crown of the road sufficiently to shed the water quickly into the gutters, and to keep the road sprinkled, so that when the winds and floods came the surface would be smooth and compact and not liable to their disintegrating influences. On the roads by the side of the horse railroad tracks the wear has been about an inch and a half during these three years, while on the roads free from these tracks the wear has been about one inch on the crown and perhaps a half inch on the sides. The cash cost of the Telford pavement laid under our direction in 1875- 76 was ninety cents per square yard. The stone was broken by a ten-inch " Blake" stone crusher at the rate of about twenty cubic yards in ten hours. The size of the stones as they came from the crusher was : 50 per cent., 2 inches size ; 25 per cent., \yi to I inch size , 25 per cent., screenings and pea dust. The cost of the crusher, engine, boiler, &c., set up complete, was about $2,500. The cost of working per' day, independent of the original cost of the machinery and interest thereon, and also independent of any royalty on the stone, was found by the contractor to be as follows : Kcpairs, lubricants, wear and tear on crusher and enorine, about $ '.00 1 Engineer, |'2 .50 ; 1 feeder, $1.50; 1 screener, .^1.5u ; 5 laborers quarrying and bieakiig 111) stones at $1.00 . 10. "50 1 team hauling scone 6.00 1 Coalhalfton ....* .'..".....*.. 2.50 Cost of preparing and crushing 20 cubic yards of 6tone S24.00 Cost of I cubic yard, $1.20. 122 CONSTRUCTION AND MAINTENANCE OF ROADS. The roads built under our direction in 1878, and now building, are the same in every particular as those built in 1875-76, except that they occupy only 20 feet in width of the crown of the road ; the steam roller was not used, and as it is very difficult to obtain an abundant supply of water in the locality, we have to rely on the rainfall for sprinkling, and do all our rolling in wet weather. A horse roller is used of 150 pounds per inch run. Some 3,000 square yards of these roads were completed one year ago, and have been, since that time, subjected to a daily traffic of about 150 wagons, principally carts, loaded with stone and dirt. The surface of the pavement is now as nearly perfect as it is possible to imagine that of a macadamized road to be. The cash cost of these roads is eighty cents per square yard. -^ CONCLUSIONS. A Telford road m^y be practically divided into two parts. 1. The foundation, which should be uniformly secure, and which should be at the same time a perfect blind drain. 2. The superstructure, which should be a durable, water-tight roof. If these conditions are complied with — if proper materials are used in the construction of the road, and reasonable attention is given to its main- tenance, the result will be as has been claimed, a durable road, unsur- passed for comfort of travel, and one to be preferred to all others for sani- tary reasons. If these conditions are not attended to the road will last but a short time. The foundation is of the first importance. It should be eight inches in depth. More than this is a waste of material, and a less depth is not suf- ficiently secure for want of proper bond. It must be laid as close as pos- sible by hand, then the interstices at the top wedged and sledged, until the small stones that compose the superstructure cannot work down, and fill the interstices at the bottom of the foundation. Too much emphasis cannot be given to this part of the work. It is not only essential to perfect sub- drainage ; it is equally important in the great saving of the cost of building the road. A loose foundation, which allows the small stones to settle down upon the large ones, will require nearly as many again of the small stones before a proper surface can be obtained, hence the cost of the superstructure will be nearly doubled. Of course, if the small stones work down among the large stones, the latter will work up the surface, and ultimately ruin the road. An excellent test of a foundation, when the substratum is firm, is to drive a loaded truck — weighing about three tons — over the pavement be- fore any of the upper courses are placed thereon ; if the foundation has been properly laid no ruts or other displacement will occur. CONSTRUCTION AND MAINTENANCE OF ROADS, 123 As to the size of the foundation stones, we prefer them large rather than small. Nothing is so dangerous as thin slabs. A large stone now and then, say ten inches wide, well bedded, seems to act as an anchor for the rest, and we have yet to find an instance where the small stones have broken loose from suci a foundation stone. In regard to the superstructure, we are convinced that if the material is crushed trap, any increase over four inches in depth is a waste of material. We found this to be the most expensive portion of the road, the cost of the eight-inch foundation being to the cost of the four-inch superstructure as one is to two. Four inches will answer all requirements as well as any greater depth, because after the metal has worn down two inches, the road, owing to unequal wear, will need to have a new coating in any event, and the amount saved in the first cost and the interest thereon, by making the superstructure only four inches deep, will keep the road in repair for many years. In regard to steam rolling, it is often questionable whether it is essential, or even desirable, in the building of Macadamized roads, espe- cially when the road is built of New Jersey trap rock. The principal action of the steam roller is to crush the stone into the crevices, and the result is, that a crust is quickly formed. On the other hand, the horse roller rattles around and shakes the small stones about, until they are firmly bedded upon the rough but firm foundation and upon each other. No crust is formed, but, on the contrary, a compact homogeneous mass, which result is much more to be desired. Ay^ain, the road bed upon which the pavement is laid often varies very greatly ; frequently a rocky bottom adjoins a soft stratum; on one side of the road may be an excavation and the other side a fill. In such a case, a heavy roller is much more likely to disturb the uniformity of the foundation than a lighter one, no matter how great care may have been taken to provide for emergency. If it be necessary to finish the surface of the pavement within a week or two, a steam roller must certainly be used, but we believe that rapidly made roads are much less durable than those whose construction extends over a long period of time. It required at least three months to finally form the surface of the roads built by us in 1875-76, while on the roads now building, some of the sections have required as much as six months. In the meantime, the surface is kept free from loose and rolling stones, so that there is no brutal pulling through the road metal. After a road has been slowly compacted in this way, we believe the surface will be found much more durable than that of any rapidly made steam rolled road. As to "bindiag," our experience has been that during the construction 124 CONSTRUCTION AND MAINTENANCE OF ROADS. of the road the less foreign material used the better, unless, perhaps, along the edges of pavement which has only an earth support. In such a case, it is necessary to bind the edges as quickly as possible, in order to prevent the sides of the road from spreading while the surface is forming. After that is accomplished, very little wear comes on the extreme edges of the road. As an aid in the rapid formation of a fine surface, a little yellow clay placed just below the upper course is almost invaluable, but when the crust is broken the danger is that the surface will soon disintegrate, while if, instead of the clay, stone dust is placed between the courses of broken stone, and a top dressmg one inch deep of screenings, such as are pre- sented herewith, is spread over the surface and is thoroughly worked into the broken stones, the surface is equally fine and much more durable; if a spot does loosen here and there, it does not spread and a little moisture quickly rebinds the loosened stones. Finally, as to the stones for the superstructure, we greatly prefer machine-crushed to hand-broken stones. 1. Because they are much more uniform in size, each having actually passed through a revolving screen. 2. Because the edges of the stones are much rharper and bind better. 3. Because from the machine alone can we obtain the screenmgs and detritus which we consider so essential for compacting the road and for satisfactory top dressing. — George D. Ansley. — My experience is decidedly in favor of steam rolled Macadam or Telford roads over those formed by horse roller ; in fact. I have altogether given up the use of the latter, and employ a 15-ton Aveiing & Porter, the result being far greater economy in the end as to outlay, and a decidedly smoother and more permanent surface is obtained. As to compacting with traffic, I am altogether opposed to it, as being inhuman toward horses and extravagant in the waste of material. I speak of the case when any considerable extent of roadway is to be covered ; but ill small repairs, or what is technically called " darning," I first pick up the margins of the depressions to the depth of an inch or two, and then flush up with stone broken to pass through a 2-inch ring ; the edges of the patch are then covered with road grit, obtained at hand and pounded with a rammer. In these repairs it is found that the horses feet avoid the fresh stone, while the wheels of the vehicles run over the patch and compact it gradually from the edges to the centre and a very good "mend" is thus made. In reading over Mr. North's valuable collection of short histories of road making, I was particularly attracted by the mention of ramming, on page 103. There is a short mention of a rammer 8 inches diameter, weighing 70 pounds. Although steam rollers are far more satisfactory CONSTRUCTION AND MAINTENANCE OF ROADS. 125 than horse rollers, it seems to me that a s'ill further improvement may be made by the more general introduction of the rammer. In all cases of roads, whether Telford or Macadam, or stone paving, or wood paving, the first imperfections are the same ; the surface may not be worn away materially, but there are depressions or concavities that hold water. Our block stone pavements get into bad order chiefly through unevenness, and a heavy expense is incurred in repairs, while the hollow parts are found to be hard and well set, and the blocks not worn, perhaps, any more than those forming the better parts of the road. A wooden pavement on one of our streets was condemned for being in hills and hollows ; although incidentally there were rotten blocks that broomed and wore away, it was found, on taking it up, that the foundation was uneven, and this notwith- standing that it had been steam-rolled before the blocks were laid on, five years before. All this tells the same tale — the earthy foundation is of un- equal density. Much more attention has been paid to the coating of stone or other material than to the lowest or earth foundation. When a new road is made, the proper form may be given to the earth foundation, and it may be steam rolled ; inequalities then showing themselves may be flushed up and re-rolled, but a roller will bridge over smaller soft places which still remain unseen until the road is completed and heavy traffic put upon it, and then we have saucer- like dips in its surface, to be repaired within a short time after the road is made ; and although the specification may require that these repairs shall be done by the contractor, the surface being thus broken, the road is never so good afterward as it would be if undisturbed. How the rammer which Mr. North refers to was used is not mentioned ; but if by steam power, it might be neither expensive nor slow. I am inclined to think that the regular stroke of a rammer is the only method of producing equal densities for roads, as well as for other pur- poses, and that the most important part of road making for its application is the earthy bottom. After the ramming to equal density, I cannot see that Telford's method is better than Macadam's for general adoption; local circumstances, however, would decide in each case. After reading through all the various descriptions, and adding my own views from observation and experience, I consider the object to be aimed at is as near as possible, a solid bed of stone. This certainly can- not be accomplished by putting on any earthy matter as binding. Broken stone in thin layers, 3 to 4 inches, chinked with fine chippings or screen- ings until full, and then watered and rolled with steam roller, will come very near the desideratum. Of course the lower strata may be of stone, less hard than the top. The size of broken stone for the upper part is 126 CONSTRUCTION AND MAINTENANCE OF ROADS. important. A 2}4''inch ring allows stone of considerable size to be mixed with lesser ones, and it is these larger ones that first get loose and move about on the surface. For the surface coating I prefer hand broken stone over machine broken, as the form is generally more cubical and less apt to become disintegrated. Gravel is much more difficult to reduce to solidity than broken stone; but where there is a large supply, and cheap, it is well to follow the principle before mentioned. The gravel should be screened, and the coarser sort laid on first and then chinked up with the finer. If this is done, and all coarse gravel kept away from the top coating, water and steam rolling will make a good road in almost any case without earthy binding. Earth matter works into mud, and should be avoided, unless the gravel is so round and movable that nothing else will keep it quiet. Where old paving is taken up, and it is proposed to put down Macadam, I consider that there is the same necessity for testing the density of the foundation, and rendering it equal by ramming. A. B. Hill. — In New Haven we have tried several plans in regard to the binding material of the Telford pavement. Using an inch of loam on the crushed stone, with two inches of screenings over that ; also using sand instead of the loam ; but the best results with us are obtained by using the trap rock screenings alone, spread on in thin layers, sprinkled and roughly rolled. This makes a very sohd, firm surface, which does not wear into ruts as soon as the pavements are top-dressed by the other methods. The roller used is the 15-ton Aveling & Porter. As the grades in New Haven are generally very light, and it is desira- ble to secure a uniform, smooth gutter, the latter is made of blue stone, 12 inches wide and not less than 4 inches thick, bedded in sand next to the curb, closely jointed, well rammed, and, after the pavement is com- plete, thoroughly grouted. A space of three feet outside the gutter stone, between the rails of the horse railroad tracks, and for three or four feet outside the rails, is laid with stone blocks. The Telford pavement is 16 inches thick at the centre and 14 at the sides, made up of 4 courses of trap rock ; the first or bottom course 7 inches thick at the centre and 5 inches at the sides ; the stones of the size and placed as usually specified for Telford foundation ; the second course, 3 inches thick, of stone simply raked out and sorted at the foot of the trap dikes (not " broken " or " crushed "), varying in largest dimensions from I inch to 4 inches, spread on the first course and rolled until solid ; the third course, 4 inches thick of " crushed " stone, also rolled ; the fourth course, or top-dressing, about 2 inches thick of screenings, spread on in three layers, each layer sprinkled and thoroughly rolled in. CONSTRUCTION AND MAINTENANCE OF ROADS. 127 The averag:e cost of the Telford pavement in New Haven, including the Belgian blocks, blue stone gutters, crosswalks, inspecting, rolling, &c., was, for 1876, $1.18 per square yard. '• 1877, 1.05 " 1878, 1. 15 E. Lavoinne, Engineer des Fonts et Chaussees (through the Secre- tary). — The criticism of Mr. North upon the Macadam roads in the City of Paris is to the effect that owing to the method of compacting, suffi- cient stability is not given to the stones to resist the traffic. Mr. Malo is quoted as sustaining this criticism. Even if the bad results in Macadam pavement in Paris were something like what Mr. Malo describes in his rather sweeping remarks, the fair inference would be, it seems to me, that the system of construction was not the best m that location on account of the heavy traffic. Macadam roads when introduced in Paris to replace the former pave- ments were considered by many engineers as a blunder, on account of the cost of their maintenance and other peculiarities. It is certain that no Macadam road, even if constructed under the best conditions, could stand the enormous traffic existing in many streets, which is not occasional, as Mr. North states is the case for some of the Boulevards of New York, but continuous and daily for most of them. As regards the construction of roads, the illustration of what Mr. North ca'ls the French system, such as he saw applied in the repairs of some streets in Paris, hardly gives an exact idea of the standard system adopted by many French engineers. They generally consider that in a perfect Macadam all stones should bear directly against one another by faces as large as possible, not by edges, and that the interstices, previously reduced to a minimum by rolling, should be filled afterwards with a bind- ing which cannot be affected by atmospheric influence nor give access to moisture. Thus far they agree with Mr. North — but they disagree with him as to what is the best binding. Instead of screenings or very small stones with the addition of dust and water, they prefer to use sand with a small quantity of chalky dust employed when compacting is at an end. They consider, contrary to Mr. North's theory, that when the stones, whose sizes vary between 1% and 2>^ inches, have been thoroughly packed together by rolling before any addition of binding, so that they move no more under the roller, and a beginning of crushing takes place, then an addition of smaller stones is useless for stability ; if very small stones like screenings were then added, they would be crushed and produce an excess of dust injurious to general stability. Sand, injected by thorough watering between the stones is not liable to that objection, since, filling all the interstices, it tends to equalize the pressures between the stones. The addition of chalky dust 128 CONSTRUCTION AND MAINTENANCE OF ROADS. diluted by water, at the end of the operation, fills the interstices between the grains of sand making with it a sort of mortar and coating for the surface. In my own experience the best results followed this method ; the consolidation of the Macadam was very satisfactory at the end, rolling not being spared before the addition of binding. Loose stones occurred only at a few points. It may be that the roads examined by Mr. North, in Paris, were con- structed in too thick layers and too hastily permit the stones, prior to any addition of binding, to have the required stabihty, much rolling being necessary for this result. This may be the reason why loose stones were seen. If the stones have not been packed and wedged previously by thorough rolling, we cannot expect binding to make them immediately compact. The system mentioned as used in New York (St. Nicholas Avenue), in which stones of from i to i}4 mches are employed for he top course, will, no doubt, do for light travel (light, not heavy carriages) ; but such pavement would very likely be destroyed by a heavy traffic, as the small stones would then be rapidly ground and disintegrated. From my own experience and that of many engineers in France, I am fully satisfied that the capital difference between the roads in the old Macadam style without rolling, and those that are rolled, whether with steam or horse power, is the degree of internal wear ; as the grinding of the stones by their recip- rocal friction or internal disintegration is much more rapid under heavy traffic with the former than the latter. In the first case the proportion of disintegrated material, detritus, to the stone is generally large after a short time ; very small in the second if proper care has been given to the work. Evidently much more consideration should be given to the internal wearing, which is of serious consequence as to cost of maintenance, than to the incomplete consolidation of the road immediately after rolling, which could be remedied by more rolling or made up afterward by the traffic itself and by removing the excess of binding material by sweeping. In conclusion, it is suggested that for a fair comparison between the different systems of constructing the roads, there should be taken into account both the quantity and quality of the traffic, and also the cost of maintenance under the same conditions for a fixed period. Conclusions might be different if full consideration were given to these points. E. B. Van Winkle. — I would say that I am familiar with the roads Mr. North has been constructing for the past few years ; that is, with their present condition, and should like to ask Mr. North if their present condi- tion bears any relation to the amount of rolling he put upon them ; for in- stance, the Southern Boulevard, which I now consider to be the best of these roads, and the one that carries the greatest traffic, did that receive the greatest amount of rolling ? n COXSTRUCTION AND MAINTENANCE OF ROADS. 129 E. P. North. — The Southern Boulevard received 0.859 ^o"^ "^i^^ P^** square yard, or 5.177 ton miles per cubic yard, which is more rolling than any other road constructed by me had, and more than any road known to me has had applied to it. The road has stood the wear very well, though part of it is exposed to a very constant breeze from the Sound, which deprives it of the protection that a layer of dust would afford. The teams on it were counted from 8 a. m. to 5 p. m., and averaged about 300, from four-horse teams, with six or seven tons to the load, to buggies. E. B. Van Winkle. — Next to the Southern Boulevard I should place the streets constructed by Mr. North in the following order as to degree of excellence, always judging by their present condition : 1st. One Hundred and Thirty-eighth street; 2d. One Hundred and Sixty-seventh street ; and last, Mott avenue. Please, if possible, state which of these received the greatest amount of rolling, and if there were any difference in the quality and size of the metal and the material used for binding. E. P. North. — One Hundred and Thirty-eighth street, which has two courses of broken stone, each about 6 inches deep before rolling, received less rolling than the Southern Boulevard ; the surface is satisfactory ex- cept in one place, where the bottom was bad and mud worked up through the metal where there are some loose stones. One Hundred and Sixty- seventh street is on a heavy grade, part being at the rate of 11 2-10 feet per 100, and the rest with 8 per 100 for a maximum. The first was rolled with both horse and steam rollers, the steam roller ascending by an easier grade. Some clay hardpan was used here in connection with the screen- ings, both 10 increase the adhesion of the roller wheels and facilitate the compacting of the road bed. The roller, a 15-ton Aveling & Porter, old pattern, ascended the grade after the application of the hardpan. On the lighter grades nothing but screenings was used for binding, and the rolling was done entirely by steam. This part of the wheelway wears much bet- ter than that portion where hardpan was used. No reliable account was kept of the amount of rolling this street received. The circumstances under which the wheelway on Mott avenue was constructed are fully detailed in Transactions, Vol. VHI., page no (May, 1879). On account of its treacherous bottom it probably received less rolling per square yard that any other road, though it was impossible to keep accounts of the amount of rolling done. All of these streets are Macadamized with two-inch trap and clean trap screenings, excepting that portion of One Hundred and Sixty-seventh street mentioned above. B. F. Morse. — The paving of the Cleveland Viaduct, west of the I30 CONSTRUCTION AND MAINTENANCE OF ROADS. river, over the arches, is laid with New York Medina sandstone ; the road- way is 42 feet between curbstones, with a double track street railroad in the centre. The ballast used was of the best quality of bank gravel spread in layers of about five inches in depth. Each layer was sprinkled with wa^er and rolled. The last layer, or that directly underneath the stone, was about two inches deep, and was left without sprinkling or rolling to receive the bed of the paving stones. The surface of the ballasting was finished to the true crown of the roadway. The pavement is laid with blocks, dressed nearly parallel on top and bottom, sides and ends, laid in courses transversely across the roadway. The courses were from three to four inches thick, and from six to seven inches in depth, and the stone from seven to twelve inches in length The stones were set close together, so that no joint was more than one- half inch open for at least two and one-half inches down from the top surface. No gravel or sand was placed between or on top of the pavement while it was being laid. After the stones had been set in place in sections of fifty to one hundred feet in length of the street a light top dressing of gravel or sand was spread over the surface and swept into the joints with a steel splint broom. The pavement was then thoroughly sprinkled or flooded with water. Then the pavement was thoroughly rammed two or more times with a paver's rammer weighing about ninety pounds ; then the pavement was again washed or flooded and allowed to dry off. The joints were then filled to a depth of three to five inches with a concrete composed of Trinidad bitumen and coal-tar cement, distilled at a temperature of not less than 600 degrees Fahrenheit, and mixed in proper proportion, so as not to soften or become brittle under heat or cold, and was poured into the joints of the pavement at a temperature of not less than 300 degrees, and then the whole surface was covered with one-half inch of fine gravel or sand, which completed the work. The pavement on the fixed iron spans was laid in the following manner : Strips of oak plank, varying in thickness from one and a half to three inches, were secured to the iron floor beams, running longitudinally, to give the proper crown to the roadway. On top of these longitudinal floor beams was laid a layer of two and one-half inch plank, joints well broken and spiked down. On top of this layer of plank there was laid two thicknesses of tarred roofing felt, or paper, laid in hot roofing cement, and the whole covered with one-fourth of an inch of plastic pitch, and over this was laid .1 layer of inch boards or sheathings, breaking joints with the plank under- neath, and thoroughly spiked down. The paving is what is usually called "Nicholson," and consists of blocks four inches long and three inches thick laid upon and in rows across the CONSTRUCTION AND MAINTENANCE OF ROADS. 131 roadway, with a three-fourth-inch strip, one and one-half inches in depth between the rows of blocks, and nailed to the flooring, the blocks breakings joints at least two inches with adjoining row. The space between the rows of blocks was then filled with concrete, composed of one part of hot undistilled gas tar to two parts of pitch, mixed with clean lake sand and fine gravel, applied hot and driven into the joints with an iron blade and heavy rammer until the spaces were even full. The whole surface of the paving and gutters was then coated with a top dressing of coal tar pitch and fine gravel, rolled thoroughly with a heavy hand roller. The best quality of seasoned white oak was used for all the wood parts of the pave- ment and plank floors. E. S. Chesbrough. — I cannot state the average wear of wood pave- ments ; I can only state that it differs very much with regard to different kinds and in different localities. You can easily see that very much depends upon the faithfulness of doing the work and the material used. In some cases in Chicago wooden pavements have lasted ten years, and even longer ; and in others they have become very rough and uneven in three or four years. I am not able to give the precise average, but of course a great deal depends upon the traffic. In the river tunnels the wooden pavements have worn out in less than two years, and where the wheels were confined very much to the same tracks they m.ake ruts in a short time. In other cases, where the streets are broad and clear, and the traffic is spread over a large space, they have lasted a long time ; in some cases ten years. It is impossible to give the rule in regard to that unless you take into account various circumstances. Edward R. Andrews. — I would like to ask Mr. Chesbrough whether at Chicago there is any very perceptible wear in wooden pavements until decay sets in } Edward S. Chesbrough. — Decidedly ; I have seen some worn down more than two inches without any apparent decay. Edward R. Andrews. — Mr. North states that a well made Macadam road, constructed with trap rock, is, after an earth road, the pleasantest and safest known. But trap rock or other really good materials for making Macadam roads are not available everywhere, and, at best. Macadam roads are only adapted for pleasure travel in parks or suburban towns, where they can be constantly watered and never allowed to get out of repair. Macadam is not adapted for general use in cities. Under heavy traffic the surface is constantly ground into powder, which rises in dust in the summer, and they are very muddy in the winter. Even in Paris, where the maintenance is most thorough, the streets being continually watered in summer in the manner described by Mr. North, and frequently washed after a day of unusual wear, and scraped by a large army of cantonniers, yet, after heavy rains, the mud is frequently nearly ankle deep, and in very 132 CONSTRUCTION AND MAINTENANCE OF ROADS. hot weather, during the intervals of watering, or in frosty weather, the air is filled with most penetrating dust. Mr. Flad describes the same state of things in St Louis ; and in Boston, when, in winter, there is no snow to cover the ground, and, on account of the cold, the streets cannot be watered, the dust is intolerable ; and in summer, where, for economy's sake, watering is neglected, a large part of the material with which the roads are made is blown into the sea. The compressed asphalte, so common in London and Paris, when con- structed as thoroughly as it is in those cities, and as that on Fifth Avenue, in front of the Hotel Brunswick, has been, is a most excellent pavement, but it also demands the most careful maintenance. No dirt should be allowed to accumulate upon it. In frosty or in damp weather coarse sand or fine gravel should be spread over the surface to give a good footing for horses— this is done abroad — and then it is not slippery. It is very quiet, and, in fact, has almost all the qualities needed in a perfect pavement ; but it can only be laid on levels, and is expensive. Stone Block Pavements are in many parts of the country the cheapest and possibly may be the best where the traffic is very heavy, but it is emphatically the worst pavement for streets of residences or wherever quiet is desirable ; and there is no question but that if the incessant din from the rattling of omnibuses, heavy teams, milk wagons, &c., from which one suffers in large cities paved with stone blocks, could be dis- pensed with by adopting a quiet pavement, the length of life of citizens would be increased and the general health improved. Such would have been the case long ago in New York, had it not been that the wooden pavements . laid during the " Tweed " days were such evident jobs. In London, wooden pavements give entire satisfaction. The earliest were not quite successful, but the defects in construction have been remedied, and now broad areas of heavily worked streets previously paved with stone are being laid with wooden blocks, which are found to wear satisfactorily. In the West, where stone for pavements cannot be had, wooden blocks are largely used ; but, as wood is cheap and can be replaced without much expense, no sound principles are followed in their construction. In the Eastern States, no one will allow that a wooden pavement can be good except when newly laid, when all agree that it is delightful. There seems to be an unwillingness, even among engineers, to give the subject the at- tention it deserves. All agree that stone pavements are a curse, and that it would be a blessing if a good substitute could be found, but because wooden pavements, as they have been made here, have not been a suc- cess, condemn them as a class. Mr. North has stated what has been the general practice in laying wooden pavements in this country. Many methods have been tried, but they have almost without exception been " laid ^'x'&s. green or wet blocks, CONSTRUCTIOiY AND MAINTENANCE OE ROADS. 133 more or less thoroughly dipped in tar, on a bed of sand, not always well rammed, with or without the interposition of a tarred pine board, with transverse joints from one to one and a half inches wide filled with gravel and coal tar," and I might add, the whole done in a most unworkmanlike manner. The results are what might have been expected. The careless manner in which the joints have been filled, has left many channels open for the admission of water, which undermines the sand foundation, so that there is an uneven subsidence under the passing wheels, and holes, small at first, but daily growing larger, appear, so that the surface is soon destroyed. The result is but little better when tarred boards are laid under the blocks. This practice of tarring wet sappy boards and blocks seems to be an in- vention to make them decay as soon as possible. It closes up the cells of the wood, so that the moisture cannot escape ; fermentation immediately follows, which quickly destroys the strength of the fibres and reduces them to punk. A pavement, constructed in this manner, would fail, of course. Thoroughly seasoned wood might be benefited by the tarring process, but green wood never. Observe how differently wooden pavements are constructed in Lon- don. Mr. North describes several methods, either of which is vastly supe- rior to any of the patented systems used here. A rigid foundation of bituminous or cement concrete is universal. This costs more than sand, but it is permanent, and will prevent the blocks from sinking under the wheels. English engineers, in discussing pavements, call the foundation the true pavement, the blocks being the wearing surface only. The " Henson " pavement, with some modifications, strongly recommends itself to my mind as the best for this country. Instead of a layer of tarred paper on the concrete, I would use a thin layer of pitch, with oil enough in it to make it permanently slightly plastic, setting the blocks upon it while hot and soft, using the strips of tarred felt between the rows, and driving the blocks together as described by Mr. North. The tarred felt would make a very close joint. Then pour melted pitch over the whole surface, taking care to fill every crevice, and upon this spread fine sharp gravel, which will work into the ends of the blocks and form a surface resembling macadam, and afford a far better footing than wide spaces be- tween the rows, which serve as receptacles for mud and dust. It is easy to keep this pavement clean. No water can penetrate it, so that it will not be injured by frost. The blocks themselves, if creosoted, will not absorb water, and if laid without spaces between the blocks, the drainage will be surface drainage solely, which is of the first importance. But the pavement would be short-lived, if green and wet blocks are used. It is not practicable to use, as Mr. North says is the case in Lon- don, " wood better seasoned than the pine generally used by house car- 134 CONSTRUCTION AND MAINTENANCE OF ROADS. penters in this country." Seasoned wood cannot be obtained in sufficient quantities here. But, what is far better, it can be preserved from decay, I have no faith in any method of wood preservation for paving blocks which does not exclude water. The blocks are so short, that any soluble preparation is quickly washed out of them, and, if not made waterproof, they are certain to absorb the seeds of destruction from the filth in the streets. The blocks should be well saturated with creosote oil, whose chemical constituents act preservatively upon the. fibres of the wood, by coagulating the albumen of the sap, while the fatty matters act mechan- ically in obstructing the pores of the wood and keep the water out. At the same time, as oil cannot be injected into wood full of moisture, the thorough artificial seasoning, which forms a part of the process of creo- soting as carried on in this country, is as useful to the timber as any of the metallic salt processes. By thoroughly creosoting the blocks, expansion and consequent throw- ing out of the blocks is prevented. They wall not shrmk or expand. The wood is also rendered homogeneous, the sap wood becoming as durable as heart wood. Looking to sanitary considerations, the creosoted wooden pavement is perfect. The carbolic acid contained in the oil is a powerful disinfectant, and as the pavement described will not absorb any deleterious substance from the surface, it has only to be kept clean to maintain the best sanitary condition. This is far from being the case with wooden pavements laid on the American plan. They soon become a mass of decaying vegetable matter, and, as their powers of absorption increases with their disintegration, they become filled with corruptible matter absorbed from the filth of the street, and as their sur- face becomes filled with holes, it is absolutely impossible to keep them properly clean. A good wooden pavement is also an inexpensive one. The cost, includ- ing a cement concrete foundation, 6 inches deep, would not exceed $3.00 per square yard. The system of maintenance adopted in London, of making it a part of the contract of construction, would insure good workmanship in laying the pavement, and a good permanent roadway afterwards. It would not be difficult to find responsible and honest contractors willing to take such a contract at a fair price. In considering this subject, one should not overlook the statistics of accidents gathered in London by Col. Haywood,* which show that a London horse will travel on granite 132 miles, on asphalte 191, and on wood 446 miles, before an accident occurs. The actual wear of wooden blocks is very slight, as long as the fibres of the wood are sound. Mr. North states that it is yi of an inch per * See full reports in the library of the Society. CONSTRUCTION AND MAINTENANCE OF ROADS. 135 annum in the streets in London, with the heaviest traffic. Mr. Geo. Frederick Deacon, Member Inst. C. E., in a paper read before the Inst, of C. E., states that, in Great Howard street, Liverpool, which is a shop street, with a traffic consisting chiefly of carriages, amounting to about 94,000 tons per annum per yard in width, the pavement was worn to the extent of* >^ of an inch in four years. This would give a life of nearly twenty years before the blocks would be reduced from 6 iHches to a thickness of 3 inches, which is still sufficient to maintain the blocks in place. In Oxford street, in London, where the traffic is equal to 300 tons per foot per day, the amount of wear has been found to be from xV to ^ inch during three and a half years. This street is laid with the Henson pave- ment. This slight wear is largely due to the fact that the ends of the fibres do not broom, and thus retain their original strength. C. Shaler Smith. — I merely wish to ask Mr. Andrews — speaking of the foundations of wooden pavements — if he is aware of any pavement being laid as upon the Cleveland Viaduct, that is, Nicholson pavement upon an iron foundation ? E. R. Andrews. — I am not aware of any except the Broadway Bridge in South Boston, where it was necessary to have a light pavement. A bituminous concrete about two inches thick was spread on the top sheet- ing and allowed to become solid ; then a thin coating of hot tar spread evenly, and creosoted spruce blocks, injected at my works wiih 12 lbs. of oil per cubic foot laid in rows yi inch apart, and the interstices filled with pitch and the surface spread with gravel. G. BousCAREN. — Can you give the cost of.creosotmg .'' E. R. Andrews. — $12.00 to $16.00 per thousand feet, board measure. G. Bouscaren. — Can spruce be treated well } E. R. Andrews. — Spruce does not absorb oil readily on account of the compact character of its fibres, yet it will take in a gallon of oil per cubic foot ; hemlock, pine, both white and yellow, and porous oak, are more absorbent. Wood which is the most destructible, because it ab- sorbs water readily, is really the best for creosoting, as, for instance, the gums and cottonwood. G. Bouscaren. — Have you any special rule for determining the amount of carbolic acid in the oil ? E. R. Andrews. — I have not taken any pains to ascertain. The quantity depends upon the character of the coal from which the gas was made, varying from 5 to 10 per cent. It has been ascertamed, however through careful experiments by a Belgian chemist, that the wood-preserv- ing qualities of creosote oil are due rather to the water-proofing imparted to the wood by the hydro-carbons contained in it than by the carbolic acid. The latter is very volatile, and were it not retained by the gummy, resinous 136 CONSTRUCTION AND MAINTENANCE OF ROADS. oil, would quickly escape into the air. In England ho reference is made to the quantity of carbolic acid contained in dead-oil to be used in the speci- fications for contract work. Carefully conducted experiments of my own with pieces of yellow pine, 8 inches by 8 inches and 9 feet long, have shown that six months after treatment they did not absorb any water dur- ing a soaking of 48 hours under water. M. Meriwether. — We made in Memphis, in 1867, what has proved to us a very costly experiment in wooden pavements. We laid there in that year and the succeedmg spring some 225,000 square yards of what is known as Nicholson pavement. The streets on which this was laid rise six inches from the side to the centre of the street. Two inches to two and a half of sand were laid down, and that covered over with an inch board longitudinally. Those boards were immersed in hot coal-tar. After that were laid cypress blocks eight to twelve inches long, with a thickness of three inches, with a cleat between them, tacked to them. About one-half of that kind were immersed in boiling tar. According to the contract it was to be red cypress wood, which is very durable above- ground, and of more than ordinary durability underground, and is found to last better than ordinary oak ; but the sap portion of that wood is very perishable, rotting within one or two years if exposed above-ground. The heart will last twenty-five years, or so, in fences. I mention this to show the durability of the material. Most of that was entirely covered with boiling coal-tar and small gravel, and the interstices filled with sand, mak- ing a beautiful pavement for about three or four years. Some portions of it, however, began to show decay in three years, where the sap of the block was put in. The contractor got in a good many sap blocks, and as soon as they began to decay the adjacent blocks were loosened, so at the end of about five years it was in many places impassable, and some blocks were entirely destroyed. The remnants of that wooden pavement of 1867 and 1868 are now there. The pavement cost us $3.89 per square yard. I am satisfied had the blocks all been heart cypress it would have been good for perhaps ten years. We have portions of the pavement now where the heart of the cypress was used, where there is no surface wear perceivable. However, we are satisfied with that experiment, and I do not think we will ever put down another square yard of wooden pavement of any sort. We are now makmg arrangements to pave with granite. E. R. Andrews. — It seems to me very clear that the reason why the cypress pavement did not last was because the blocks were dipped in tar. It is not at all probable that these blocks were perfectly seasoned, because seasoned lumber cannot be found in this country for paving purposes, hence the sap enclosed within the wood by the tar soon fermented and the fibres rapidly decayed. If the blorks had been laid without being dipped in tar I think you would have had a very fair pavement now. CONSTRUCTION AND MAINTENANCE OF ROADS. 137 I would like to ask as to the condition of a pavement in Washington called the Flannigan pavement, with cypress blocks sawed from round sticks and laid promiscuously, large and small together, the spaces being filled with pitch. I have understood that that pavement has stood well. J. E. HiLGARD. — That pavement has done the best of any in the city. It was tried as an experiment on Third street, near the railway. The city of Washington has made very extensive experiments in the matter of wooden pavements. Nothing was done to preserve the blocks. They were hemlock ; none of it has lain in tolerable condition over four years ; much of it had become intolerable even before that time. I think the work was badly done from there not being proper supervision. An immense amount of work was undertaken to be done within a limited time. It was the most disgraceful failure of wooden pavements ever known, and it has been a case of unprecedented decay. None of I he streets were in a fit condition to travel over after four years ; most of them have been replaced by concrete pavements. With us the experiment has been a very expensive one. Climate may have had something to do with it, for it is very warm in summer and we have very frequent showers, but certamly the decay was unusually rapid. E. R. Andrews. — In 1869, Columbus avenue, in Boston, was paved with wood ; every one who had any patent pavement was allowed to put down a piece ; one section was laid with creosoted blocks, but very imper- fectly prepared. All the pavements were taken up and the street repaved with the Trinidad bitumen in 1877; but a small delta of the creosoted pavement was left, which is still sound and in good condition. M. Meriwether. — I did not mention that about one-half of the pavement of which I spoke was laid with planks dipped in boiling tar, and after making about one-half of it the very difficulty suggested by Mr. Andrews arose, and we ceased to immerse the blocks, upon the theory that if the under side was covered with tar it would cost more, so they stopped that process and laid the balance in the other way, and after the planks were down they covered the surface simply with coal tar, upon the theory that the bottom of the planks, not being concealed, the acid would go down ; but we did not discover that it made any perceptible difference. It would probably have been satisfactory if the blocks had been heart wood, but the sap of the blocks decaying, led to their destruction by the wheels passing over it. It was an utter impossibility to have seasoned wood for such an extent of pavement — some 225,000 square yards, hid at once. The wood was not in the market, and no one could afford to keep such a stock on hand. The result was that the wood was brought di- rect^ly from the mills and put down within two or three months from the time it was taken from the stump. I do not think any process short of 138 CONSTRUCTION AND MAINTENANCE OF ROADS. thorough seasoning, or some process of drying quickly by steam, would do any good. We found it impossible to get the heart cypress entirely, and the sap wood would decay in two or three years. The blocks covered the surface and prevented the water passing down, but it may have passed on the side. They merely covered the surface with tar, and some little water might find its way down the side of the block. The spaces between the blocks were thoroughly rammed with small gravel, with sand with it, and the surface covered with coal tar. C. Shaler Smith. — I have recently made some experiments for the St. Louis Bridge, which illustrate in a marked degree the action of those preservatives depending on carbolic acid for their antiseptic value. Find- ing the wooden stringers of this structure beginning to rot at the ends and other points of support, while the remainder of each stick continued sound and untouched by decay, I tried to arrest the rotting by the injection of creosote containing ten per cent, of carbolic acid into all these timbers which showed signs of decomposing fibre. The effect was remarkable. Sound wood was unharmed, but where decay had already commenced the acid seized upon the wood and converted all parts affected by rot into a brown cinder, in many cases absolutely destroying the bearing value of the stick. The experiment was extensively and exhaustively tried, and I am satisfied that while creosote is excellent when properly applied to per- fectly sound lumber, it will not arrest decay when once started, and in many cases will destroy all the unsound parts of a stick. And also, that in th^ use of cresote, the proper proportion of carbolic acid is a very important element, and should be fixed by specification whenever this system of treatment is used. I have likewise continued experimenting on other methods of preserving wood, three of which have given good results. The first is the " Thilmany, old process," This consists in impregnat- ing the wood with sulphate of copper, and subsequently with the chloride of barium. The chemical action of the two salts fills the pores of the wood with the preservative chloride of copper, mechanically fixed in posi- tion by the insoluble salt, sulphate of baryta. The second is the " Thilmany, new process."* Here the first impreg- nation is sulphate of zinc, the second chloride of barium, and the resulting salts, chloride of zinc fixed as before by sulphate of baryta. The third is known as the tan-zinc process. The first impregnation is with chloride of zinc dissolved in a solution containing 2^ per cent, of glue. This is followed by an injection of a tannin solution which precipi- tates the glue, forming tannate of gelatine, a perfectly insoluble com- * For specifications of this process, see Appendix No. 6, CONSTRUCTION AND MAINTENANCE OF ROADS. 139 pound, and which fixes the chloride of zinc so thoroughly that it cannot be extracted either by boiling or steaming. I am not now prepared to state which of the three processes is the best, as our experiments are still going on. It may be safely asserted, however, that no system of treatment de- pending on a soluble salt, as in the Burnett or Boucherie processes, is of any value unless the salt is fixed in the wood by a subsequent injection which will fill the pores with an insoluble substance. I have procured specimens from various Burnettized bridges, and the analysis has shown in every case that the zinc had been entirely washed out of the wood. In treating wood by either the cresote or metallic salt systems the anti- septic injection is virtually worthless unless the wood has been previously ^ Trachyte on Asphalte corn- Broken Broken prime* on Stone. Concrete. Stone. Wood. Concrete. Thickness of pavement, inches 7.1 7.1 7.1 ? 2.36to2.76 " "■ foundation 6.3 6.3 6.3 ? 9.7 Cost of construction $4.50 $5.05 $5.50 $3.00 $4.35 Total cost of mainteaance 2.40 1.80 3.00 6.00 3,00 Aggregate cost of 15 years, averaging to one year, cents 46 .45 .57 .60 .49 The paving stones of Paris are described in " Romberg's Zeitschrift f. pract. Baukunst," 1878, as follows : According to the specifications a distinction is made between large and small blocks. Large blocks to be 7.9 to 9.2 inches long, 6.3 to 9.2 inches wide and 7.9 to 9.2 inches high. Small blocks to be 6.3 inches long, 3.9 inches wide and 6.3 inches high. The latter, ''paves de petit echantillon" are preferred of late. Differences in size to 0.4 inch are admitted. On account of the bond, a certain percentage to be blocks one and one-half times as long as specified above, "boutzsses." According to the dressing, two qualities are distinguished : smooth and rectangular blocks for joints of only 0.2 inch, and rough ones for joints up to 0.6 inch. The material is sandstone, "gres d'yvette des Vosges" or "de I'Ourtke," and porphyry from Belgium and Bavaria. This porphyry, however, has not given satisfaction, wearing too smoothly. The price is $44 to $125 the thousand, and $8 to $13 additional for dressing. The Macadam is being replaced where annual repairs exceed 50 cents the square yard. * Asphalte comprime la the French term for the codq pressed powder. CONSTRUCTION AND MAINTENANCE OF ROADS. 145 As to the cost of the Paris pavements, the following notes are from "Annales des ponts et chaussees," 1877 and 1878 : Pavement. Macadam. Asphalte. Cost of construction S2. 55 to $3.45 ? $1.93 to $2.42 Annual cost of maintenance, cents 9.6 29.0 17,7 The wear of Macadam, amounting to 23.37 cubic yards to the mile and 100 horses. Annual cost of maintenance to the square yard : 1872-5. 1876. 1878- Pavements, cents 7.7 8.2 8.5 Asphalte, '■ 19.8 20.9 20.4 Macadam, " 29.0 34.0 32.2 The watering with carts costs : On Macadam 19.3 cents to 1,000 square yards. On pavements 9,6 " " " J. B. Dumas, Assistant Engineer of the City of Paris, published com- parative estimates in " Nouv. Ann. de la Constr.," 1878-79, from which the following data are compiled : Price to Cost of construction. the yard. Pavement of rectangular blocks "firres," ^.9 by 6.3 by 6.3 inches $3.22 Macadam of silex . 1.61 " " meuliere 1.84 " " porphyre 1.98 Asphalte comprlme, 2 inches thick on 3.9 inches concrete. Using for the latter hydraulic lime 2 . 98 " " Koman cement 3.08 " Portland 3.15 Each inch of asphalte above 2 inches additional 1.05 Wood pavement, Trenaunay 2.76 Norris 4.31 Annual cost of maintenance and repairs: Eapaving 24 to 64 cents. Asphalte, roadway 21 " '• crossings 32 " " sidewalk 4.8" Macadam, silex 47 '' '• meuliere , 55 " " porphyre 129 " Wood pavement .56 " Both systems of wood pavements failed in streets with high traffic. Experiments with asphalte coule* have shown its unfitness for wagon traffic. The Engineer, 1878, Vol. XLVI., p. 358, ascribes the invention of the Macadam to John Lochhead in 1794. J. J. R. Croes. — Referring to the amount of water used for keeping down the dust on Macadamized roads (p. 82), the following may be of interest. In the year 1872 an account was kept of the water used on the drives in the Central Park in New York City. The length of carriage ways is 9.435 miles, of widths "froa: 30 to 60 feet, averaging 54 feet. The area occupied, including spaces for car- riages in waiting, is very nearly 250,000 square yards. The carts used fcr watering are in the form of a segment of a cylinder of 35 inches diameter, * Asphalte coulu (poured) is the French term for mastic. 146 CONSTRUCTION AND MAINTENANCE OF ROADS. the height being 26;^ inches and the chord 20 inches. The barrel is 90^ inches long, and contains 40.7 cubic feet of water. During the season of 1872, from April ist to October 31st, the roads were sprinkled on 136 days, using 81,30$ barrels of water, or 3,309,114 cubic feet, an average of 24,332 cubic feet per day, or 97 >^ cubic feet per day for each 1,000 square yards. The greatest amount used in any one day was on July ist, when the temperature ranged from 'j'j degrees to 93 degrees F., and 929 barrels or 37,810 cubic feet of water were used ; an average of 151 X cubic feet per 1,000 square yards. The next greatest amount used was on June 22d, when the temperature ranged from 70 degrees to 86 degrees F., and 890 barrels or 36,223 cubic feet of water were distributed ; an average of about 145 cubic feet per 1,000 square yards. At least one-half of the area watered was sprinkled twice as often as the other half, in consequence of its greater exposure and the greater travel upon it. I am informed that during the summer of 1879 the carriage way of Tifth avenue from Twenty-third to Thirty-fourth streets, 0.55 mile in length and 40 feet wide, embracing 12,907 square yards, was kept watered by six carts holding 70 cubic feet each, and making from three to six trips per day. This would make the amount of water used from 97.5 to 195 cubic feet per 1,000 square yards. The pavement is of trap blocks. E. B. Van Winkle. — Referring to Mr. North's paper : The form of roller proposed for the upper layers of earth roads, namely, large and smaller sized disks placed alternately on the axis of the roller, I have £ een used with excellent effect on an embankment, and it could doubtless be so used for the foundation of earth roads, but is unsuitable for surfacing and xoad maintenance. The ridges left by the use of this form of roller would tend to carry surface water longitudinally instead of the shortest distance transversely to the gutters. I believe it would be found very efficacious and economical in the main- tenance of earth roads to have the regular passage over them — one or XQore times, according to their importance — of a moderately heavy two- liorse roller a few hours after the cessation of rains. About one roller to ■eFery twenty miles of ordinary road should be kept provided. Referring to page 65 : I should think it questionable whether the addi- tion of hard pan to a clay road would be of use. Referring to pages 68 and 69 : It would be interesting to know the results of a combination of the first and last of the systems of rolling Macadam roads enumerated by Mr. North, that is, steam rolled and traffic made. I would suggest that the steam roller be first used without bind- ing material, or with very little, to bring the road metal to a passable sur- face, and then open the road to traffic. CONSTRUCTION AND MAINTENANCE OF ROADS. 147- My experience coincides with that of Mr. North — that the hardest kind of stone, if of the proper size, will produce a firmer roadbed when traffic made, without softer binding material. Referring to page 71 : The reason why the Macadam in Basnat street, Liverpool, does not show the wearing qualities of a well-puddled trap road I conceive to be not on account of the binding material — coal tar, pitch, &c. — but owing to imperfect consolidation due to hand rolling. I have no doubt that, the rolling being equal in all cases, a binding material of pitch as described would give better results than where cement^, clay, or " hoggin " were used, as less water would reach the foundation, . and the pitch would have more elasticity, giving somewhat without break- ing or crushing. Referring to page 72 : M. Malo's picturesque description of the Macada- mized streets of Paris will apply with equal force to London or New York. As far as I have any experience. Macadam pavements are a failure for city streets, except in some isolated cases where the traffic is merely nom- inal, or where all other considerations except pleasure driving are out of the question. Referring to page 7^ : One great reason for the unexpected success of Mott avenue was, in all probability, that the heavy rolling over the sat- urated fresh filling of earth of the road (some four or five feet in depth) most thoroughly compacted it, hence giving subsequently a very solid foundation for the Macadam. Referring to pages 81 and 82: The transverse section of a pavement is most important. The general tendency is to give too much crown to- the pavement. In streets where there are horse railroads this crownings has generally become excessive, the trackmen tending always to raise the. track regardless of any established street grade, while the city employes who repair the pavements meekly assume that the track is at grade and pave flush with it, while at the same time the curb is maintained at grade or settles below it. It would seem proper that the authorities in charge of street roadways should, at the time a railroad is being built, determine a proper profile for it. This profile should be filed, and the railroad forced to conform to it. Another fallacy is, that an excessive amount of crowning adds to the strength of the pavement on the principle of an arch, the paving blocks, being the voussoirs and the curbstones the skewbacks. The absurdity of this illusion is readily apparent if we conceive of an arch of 30 to 60 feet span with a versed sine of one foot or less, skewbacks half a foot thick resting on compressible earth, and, more wonderful still, the voussoirs in contact only at the extrados. The greater the crown given to a pavement the less will the depressions resulting from poor paving be noticeable on account of holding water. 148 CONSTRUCTION AND MAINTENANCE OF ROADS. In an earth road the transverse slope should never be less than the longi- tudinal slope. The restriction I consider unimportant in a stone block pavement, as with this class of pavements there is no danger of ruts being formed by running water, while it is quite desirable to have the rainfall scour quite an extent of the pavement surface before reaching the gutters. Gillespie says that the proper section of roadway surface should be formed by two planes inclined from the gutters upward towards the centre of the roadway, with their intersection rounded by a slight curve. That this is correct I have tried to believe for a long time, but obser- vation convinces me that it is not the best form. The arc of a circle is practically the best cross section for street pavements. If not from choice, at least from necessity, the bulk of travel is along the centre of the street, the portions on each side next the curb being occupied by vehicles stand- ing. With a section of the arc of a circle the centre of the roadway is al- most level. Another advantage is, that while the gutters are running full, the width of deep water is narrower than when the surface is an in- clined plane. Referring to page 83 : I fully agree with Mr. North as to the excel- lence of granite pavements in England. London, particularly, excels in the quality of its stone block pavements. I have seen nothing elsewhere equal to them for streets of heavy traffic. Their great superiority arises principally from their concrete foundations. It is surprising that similar foundations are not always used when the streets in the business portion of the city are relaid with stone blocks. The filling of the joints between the blocks with pitch I think would be a decided improvement upon the London plan of grouting. Referring to page 84 : Wood pavements, as far as I have any experi- ence, have been without exception a failure. I can conceive that creosot- ing the blocks and filling the joints with bitumen would prevent decay, and thereby materially lengthen the life of this class of pavements, but, so far, nothing has been — and in all probability never will be— invented that will prevent wood, when subjected to an incessant impact and attrition of iron horseshoes and heavily loaded steel tires from acting as wood — that is, quickly wearing down. The pits in the surface of wooden pavements have been proved by borings to be due much more to the actual wearing off of the wood than to settlement. Referring to page 97 : My recollection of those sidewalks in Paris covered with asphaltic mastic (" bitumen" so called) is, that they are not very satisfactory. During July and August almost every footstep left an impression in the mastic, and in winter they were excessively muddy, and had generally sunk out of plane. Have any experiments ever been made with the bituminous limestones CONSTRUCTION AND MAINTENANCE OF ROADS. 149 found in this country, to use them as paving material in tbe same manner as the regular asphalte ? ^ John Bogart. — Experiments were made some years ago in Chicago with a peculiar limestone, which it was thought might be utilized in a manner similar to the imported asphalte. The result was a good Mac- adam pavement, but apparently the impregnating matter had no advan- tageous effect — my recollection is that it was petroleum rather than bitumen, and that it did not exert any cohesive force. C. C. Martin. — The Smith Hydraulic Stone Crusher as now manu- factured possesses two peculiarities which render it superior in certain respects to former patents : First. — The power is applied through an hydraulic cylinder, which has connected with it a safety-valve. Second. — The opening through which the stones pass after being crushed is wider at the bottom than at the top, as shown by the cross- section at c c. These are the two essentially novel and good features of the machine ; all of the rest are simply mechanical arrangements for transmitting the power from the engine to the machine, and may be arranged as here shown or in any other way. In this machine a is the hydraulic cylinder, b is the frame, c is the movable jaw, ^the toggle, e the hydraulic ram, /the plunger, g the connecting rod, h the band -wheel, k the fly-wheel, /the stationary jaw ; the section ^ ^ per cent, of pyrites, which may become the cause of failure in employing this material. The heat to which it is sub- mitted may cause it to lose half of its sulphur, and be transformed into protosulphate of iron, an oxydizable material, which by exposure to the air is transformed into a soluble sulphate of iron ; disintegration may result from this a short time after putting it in place." Mr. H. F. Starr, of the Columbia College School of Mines, kindly made an analysis of some Limmer asphalte, which gave the following result: Bitumen 8.26 Clay 4.98 Carbonate of lime 56. .54 Carbonate of magnesia 27.01 Sesqui-oxide of iron 3.21 100.00 This is the only analysis I have seen of an asphalte that will not com- press, and the only one, excepting the Maestu, in which there is over one per cent, of carbonate of magnesia. CONSTRUCTION AND MAINTENANCE OF ROADS. 155 M. Malo gives analyses of seven different cargoes of crude Trinidad bitumen. In each case the samples were thoroughly dried, losing from 32 to 38 per cent., after which the average of the analysis was bitumen S^%> and clay 48^ per cent. The greatest percentage of bitumen in any sample was 57.55, and the least 45. In addition to the description of the hydraulic crusher furnished by Mr. Martin, a mention of the new Blake crusher may be of interest. See figure. In it the old cast-iron frame is replaced by steel rods and a wooden frame, so cushioned that the fly-wheel, in case of abnormal resistance, can make a part of a revolution. The pitman, which is above the driving- axle, can be lengthened or shortened, so as to increase or diminish the stroke of the jaws, and the length of the toggles has been increased. It is probable that these changes will reduce the expense of stone-breaking by diminishing the breakage account, which, particularly with trap rock, is a serious item. Mr. J. L. Gillespie, C. E., gives me the following as the cost of break- ings 15,150 cubic yards of limestone during 1874-5-6-7, for the concrete used in the preservation of the Falls of St. Anthony. The machine, an 8-inch by 16-inch, old pattern Blake, was run by water power, for which there was no charge. The cost and quantities were as follows, the stone being delivered at the breaker : 18T4-5 3,452 cubic varda at, 1875-6 8,284 18T6-T 3.414 .41. .81. f .18. cents. 156 CONSTRUCTION AND MAINTENANCE OF ROADS. One cubic yard of stone produced about two cubic yards of broken stone, the void spaces in which amounted to 50 8-10 per cent. The break- ages were confined to some rubber springs, one back block, and two sets of jaws and cheeks. The cost of breaking trap on the Palisades is given as follows, the stone being sledged, to go into the jaws readily. Two crushers deliver 35 cubic yards of 2-inch stone per day, when working well ; 1 5 per cent of the time is lost by breakdowns. COST. 1 engineman and fireman, at $2.50 $2.50 2 laborers, feeding 1.25 2.50 2 " screening 1.25 2.50 *ij 50 Coal, 1 ton 3.'50 Oil and waste 1 .00 Breakages. 5.00 $17.00 or, say, 57 cents per cubic yard. On Snake Island three crushers were arranged in a row, and the broken stone was carried by an endless belt to the revolving screen, whence it fell into the bins, so that no screeners were employed. The engine had one cylinder, 8 inches by 24 inches, and was running with 80 pounds of steam. The product was said to be 180 cubic yards per day when there was no breakdown. COST, 1 engineman and fireman, at $2.50 $2.50 3 laborers, feeding 1.25 3,75 $6.25 2i tons of coal, at $8.50 8.75 Oil, etc 2.00 Breakages 15.00 $32.00 Allowing for the 1 5 per cent, lost by breakdowns, the cost would be about 21 cents per cubic yard. At another place on the Hudson, two crushers, set face to face, 9-inch by 15-inch jaws, could deliver at the rate of 120 cubic yards per day, when no trouble occurred, but 100 cubic yards was a fair average. COST. Engineman and fireman ^ . . . . $2.50 3 feeders 3.75 2 screeners 2.50 $8.75 U tons coal, at $4. 6.00 Oil,etc 2.26 Repairs 10.00 $27.00 or 27 cents per cubic yard. Note. — A detailed statement of the cost, in time, of breaking stone is given in the Memoir on the Construction of a Masonry Dam. by J. J. E. Croes. Transactions o^ The American Society of CivU Engineers, No. GUI., VoL VIII., page 356 (February, 1875).— [Editor. I AD VERTISEMEXTS. 157 AVELING & P0R7^E:R STEEL STEAM BOAD-ROLIER. The Only Successful Steam Road-Roller ever Built. Messrs, Aveling 6^ Porter were Awarded the First Prize Gold Medal at the Paris Exposition, i88p. ^^ BARNARD CASTLE ^^ Patent Street Sweeping Machines, Street Scrapers, etc. -6,000 BUILT. ^W. C. OASTLER, Consulting Engineer on pighways, 43 e;xchange: puac^, ne:w york city. 158 ARTICLES ON STREETS, HIGHWA YS AND INDEX TO READING ARTICLES ON Streets, Highways and Paving Materials, IN ENGINEERING NEWS. Note —This index refers only to reading articles of greater or less length on these various topics. Much further information as to prices paid in various localities will be found under the head of "News of the Week." Numerals refer to the page and Roman letters to volume. Asphalte: Val de Travers, 517, viii. An Ancient Pavement, 191, xiii. And its Application to Street Paving, by E. B. Ellice- Clark, Assoc. Mem. Inst. C. E., I5i, 202, vii. Antiquity of, 58, xi. Pavements, 129, xiii ; 39, 44, xix. New York Pavements, 169, xxii. For Paving, 291, xxii; 28, 136, 150, ix. Technical Uses for, 129, xviii . And Concrete Paving, 473, xxii. Effect of, on Workmen, 47, xiv. Deposits of California, 27, xvii. French Rock, 253, xiii. Kentucky, 99, xx. Italian, 242, xiv. Roadways of Berlin, Leon Malo, 329, 346, 94, xiii. Barber Asphalt Co. vs. James Brand, 119, xx. Beacon st., Boston, Improvement, 410, xix. Berlin Pavements, 261. xix. . Berlin and Paris Pavements, 57, xxii. Blast Furnace Slag for Paving Blocks, 118, xviu. Brick Street Pavements : Brick Street Pavements, 90. 296, 320, xvii; 330, xiv; 99, 593, 596, 601, xxii. In Bloomington, 111., 552. x. In Toronto, Can., 17, xviii. In Berlin, 167, 31, 304, xii. Boston Street ImDrovement. West End. 292, xviii. Highways: Country, Apr. 28. 101, iv. Construction and Maintenance of Public, by E. B. EUice-Clark, C E., 378, 382, iii. Construction and Maintenance, 536, xix. in the United States, 9, xix. Highway Obstruction, Decision on, 454, xix. House and Street Drainage of Philadelphia, Condensed from a papei by R. Hering, read before the Engineers' Club of Philadelphia, 91, v. Pavements: Asphaltum, How Made, 76, xi. St. Louis Asphalt, 357, 572, x. Asphalt, 463, xx. New Orleans Asphalt. 491, x. Brick, 94, 275, 471, 554, 588, xxi. . Cedar Block, 282, xxii.: 494, xxi. Cedar in Toronto, 360, ix. Creosoted Wood, 427, xxi. Composite. 149, xi. Description of Granite Block, of Providence, R. I., Laid in 1880, 45, ix. Granite, 11, xii. Specifications for Laying Granite Block in Washing- ton, D. C, 334, V. Granite in London, 268, xviii The Grano-Metallic Stone, 234, xiv. The Guidet, 107, 132, ix. Impervious Street, 138, ix. PA VING MA TERIALS IN ENGINEERING NE WS. 1 59 The Kerr, 30, xii. Movable, 479, xx. Berlin Wood, 34, xx. Buda-Pesth, 275, xxi. Here and Abroad, 186, xiv. In Detroit, 348, xxii. Houston, Tex., 49, 110, xxi. In Kansas City, Mo., 5i4, xix. In London, 295, v . New York City, 588, xxi. Pennsylvania Avenue, Washington, 323, xxi,; 272, v. The Pelletier, 51, ix. Suit in Pittsburgh, 357, xxi. In Philadelphia, 341, xix. ; 299, xxi. Cost of Wood in St. Louis, 102, xiii. Of American Cities, 322, xxii. In Washington, D. C, 323, xx. Relative Merits of, 475, xix. Macadam, St. Louis, Mo., 216, xxi. Macadam vs. Cedar Block, 416, vii. And Paving, 93, 592, xxi. Law, Pennsylvania, 395, xxi. Foreign Practice in, 317, xviii. Los Angeles Cement, 362, xxii. Effect of Heat on Cement, 17, xviii. Our City, 223, xviii. Cost of, in N. Y., xiv A New, 161. V. Street Pavements, Dec. 1, 337, iv. An exhaustive re- view of the sub.iect by Mr. Robt. Moore, C. E., St. Louis, before the University Club. Faults and ex- cellencies of the various systems, with estimates of the respective cost of each. May 6, etc., 146, 163, 170, 179, iii. Abstract of an article by Gen. Q. A.Gilmore in the N. Y. Tribune, Feb. 19, 57, iii. Past, Present and Future, a paper by Jno. H. Sarerent, Read before the Cleveland Club of Engineers, xviii. An extract from a report of F. Shanly, City Engineer, Toronto, Ont., iii. In Chicago, 224, xviii. In St. Louis, by Thos. K. Mackland, before Soc of C. E., Feb. 18, '85, 355, xiii. For Heavy Traffic, 257, v. Of Pans. Translated for Inst. C. E., by D. K. Claik, Oct. 17, 334, V. In East Saginaw, Mich., 3, xviii. In Paris, Report by the Chief of Roads and Streets 191, V. Of Washington, D. C, Annual Report on, 297, xviii. Of San Francisco, 321, ix. In Chicago, Cincinnati, Philadelphia and Baltimore, How Paid for, 132, xiii. Of Kansas City. W. B. Knight. Paper before C. E. Club, Nov. 29, 285, xii. Philadelphia, 168, 271, xiv. ; 217, xix. In Plainfield, N. J., 15, xvii. Paving: Brick for Street, xx. "Iron" Brick for, 395, xxi. A New Material for, 257, xiv. Road Metal and Setts in, 224, xx. Specifications, HoTiston, Tex., 396, xxi. Pitch Lake. Trinidad, 501, xxi. Report of Board of Experts on Street Paving, in Philadel- phia, xii. V Paving Blocks, Buda-Pesth, 494, xix. Paving Bricks, Bitumen, 203, xxi. Race Track Construction, by Chas. Holmes, E. Saginaw Mich., 242,259,266, vi. Roads: Cost of Bad, 102, xiii. Value of Good, 449, xxi. Common, 36, iii. Good County, 89, xiii. i6o ARTICLES ON STREETS, HIGHWA YS AND Our Country. 236, 269, xvii. Gravel, Senator Washburn on, 487, xix. And Road-Making, by W. B. Sears, Ch. Eng. F. & P. M. R. R., 85, xi. Making and Repairing, 314, xiv. Building, 381, xxi. Legislation for the American ^ tate, 203, 538, xxii. Specifications for Laying Macadam, 364, v. Macadam's Improvements in Making, 80, x. Width of, 186, xxil. The Construction and Maintenance of, by E. P. North, C. E., read before Am. Soc. C. E., April 16, 1879, 228. 235, 243. Rollers, 251, vl. The Construction and Maintenance of Public, an English blue book, 223, Ix. Construction and Maintenance of French, 139, xxi. Construction and Repair of, 324, xxi. And iiridges in Georgia, 132, 101, xiii. Convict Labor in Georgia, 134, 444, xxi. Cost of Grading, in Minnesota, 271, xiv. Resolution of Illinois Highway Commrs., 327, xix. French, 160, 183, xxi. Illinois Laws relating to, 310, x. Making, in China, 6, xix. Law in Georgia, 329, xxi. In Illinois, 487, xix. In Illinois, Condition of, 145, xxii. In Long Island, Macadam, 529, xxii. In Massachusetts, 25, xxi. In Virginia, by D. H. King, 340, v. Improvements of, in Massachusetts, 317, xxi. New Jersey, 77, 512, xxii. Improvement of, in New York, 373, xix. In Pennsylvania, 25, 289, 305, xxi. Public, Their Construction and Repair: Seven Ques- tions by a Louisiana County Surveyor, 13, iii. Improvement of Prairie and Streets, by T. J. Nicholl, C. E., read before C. E. Club of N. W., Sept. 3, 1878, 310, V. Making Prairie, 193, v. Private Roadways and Streets in England, 407, xiv. Michigan Ave., Chicago, Improvement of, 367, vii. Riverside Avenue, N. Y. City, Improvement of. Speci- fications, 326, 334, 342, iv. Road Roller, Aveling & Porter, 221, xxii. Road Making, The Science of, by Clemens Herschel, a First Prize Treatise awarded by the Mass. State Board of Agriculture, 148, 156, 164, 169, 176, 185, 194, 202, 213, 221, 229, 235, iv. Road: Pike's Peak Wagon, 152, xx. Law in Roanoke, Va., 110, xxi. Bills, Penna.. 299, xxi. Specifications for Plank, 437, xxi. Shell, in Louisiana, 423, xix. Street Cleaning: Street Cleaning, 77, v Of Paris. Translation by L. Soulerin from the French of M. Vaissiere, Ch. Engr. Roads & Bridges, and read before C. E. Cluh of N. W., June 18, 215, v. In Paris, 238, viii; 94, xvii. Bill for N. Y. City, 246, 247, viii. And Maintenance, 75, xiv. In New York, 409, xiv. And Garbage Removal in N. Y., 394, xiii. English Street Cleaning Items, 280, xiii. ■ In Montreal, 57, vi. In Vienna, 285, xix. Street Sweeping; Street Sweeper, 179, 210, xviii. Street Sweeping, 476, xxi. In London, 151, iv. In Buffalo, 269, xviii. In St. Paul, 161, xiv. PA VI NG MA TERIALS IN ENGINEERING NEWS, Street: Excavations in Washington, D. C, 410. xxii. European House-Building and, 408, xix. Lights, Providence, R. I., 305, xvii. Refuse Disposal in London, 271 xvii. Sprinkling, Bournemouth, Eng., 285, xix. Sprinkling, 21, 436, 497, xxi. Naming, 249, 250, xix. Names, London, 506, xix. Naming in Mexico, New Method of, 44, xx. Renumbering City, 105, 115, viii. Maintenance in N. Y. City, 456, xviii. Maintenance in Paris, 13, xvii. Monuments, 4, xvii. Grade Intersections. 134. 150. xvii. Sign, 70, xvii. Commissioners, Boston, 308, xxi. Snow Removal in Paris, 17o, xvii. Act, Penna. Borough. 395, xxi. Crossings, Law of Over and Under Grade, 327, xix. Railway Accidents, 184, xix. Tramways, by Robinson Souttar, from Proceed- ings Institution Civil Engineers, 304, 312, iv; 322, 329 339, 346, iv. Curb and Gutter, Philadelphia, 38, xvii. "Work, Decision on, 327, xix. Bill, Ives, 516, xxi. Street Refuse in Glasgow, Disposal of, 97, xii. Street Rails and Pavements, 80, xix. Streets: Resistance to Traction in, 106, ix. Length of London, 11, xii. Street Improvement, Elm St., N. Y , 134, xxi. Street Improvement, Laws for, in Cities, 71, iii. Streets, The Fee of, 366, ix. Streets, Olden Time, 24, xx. Street Paving, 256, 265, 350, vii. Street Paving, Special Assessments for, Court Decision Sustained, 101, xiii. Street Paving Specifications, 159, 227, ix. Specifications of Western Ave. Improvement, Albany, N. Y., Mar. 10, 63, iv. Sidewalk, Repairing of, in Washington, D. C, 309, ix. Subways and London Streets, 285, ix. Steam Rolling for the Maintenance of Roads in the Ardennes, Annales des Ponts et Chaussees, 447, ix. Sheet Asphalt Paving, 102, xifi. Slag Paving Blocks, 302, xiii. The Saddler Brick Pavement for Streets, Col. Flad's opin- ion of, 587, X. Tar Concrete Sidewalk, 539, xxii. Tar and Gravel Concrete Street Gutters, 130, iv. Telford Macadam, 221, xxii . Turnpikes in Lancaster Co., Pa., 256, xiii. Turnpiking and Underdraining Common Roads, by R. C. Carpenter. C. E., Lansing, Mich., 300, 306, iv. Wear of Horse Shoes on Macadam, 28, viii. Wood Pavement3 : Of Chicago, by E. A. Fox, C E„ a Paper read before the C. E. Club of N. W., Jan. 2, 1878, 14, 22, v. Of Chicago, 287, iv. In the Metropolis of London, by Geo. Henry Stayton, Proceedings Inst. C. E., 242, 253, 265, 277; 7, xii. In Berlin, 156, xi. In Paris, 462, 552, x In London, 531, 580, x. Wood as a Paving Material under Heavy Traffic. O. H. Howarth, Assoc. Inst. C. E. Proceedings Inst. C. E., 212, vi. Wood, Treatment of, for Street Pavements, by Thos. J. Caldwell and Thos. D. Miller, before St. Louis Club of Engineers, March 4. 1885. 322, xiii. Wood vs. Stone Pavements, 193, xii. Woud Pavement in Dalla,, Tex., Specifications for Bois D'Arc, 178. x. i62 AD VER TISEMENTS. RUDOLPH HERING, M. Am. Soc. C. E., M. Inst. C. E., M. Can. Soc. C. E., 277 Pearl Street, New York, Civil and Sanitary Engineer. Designs for all work pertaining to Sewerage and Water Supply of Towns. SPECIAL ATTENTION GIVEN TO ROADS AND PAVEMENTS. F. A. DUNHAM, Civil Engineer. Engineer of Union County (N. J.) Road System, No. 7 Park Avenue, Plainfield, N. J. SPECIAL ATTENTION GIVEN TO THE PAVING AND IM- PROVEMENT OF STREETS AND ROADS. Plans, estimates and specifications for engineering wort-s furnished and construction superintended. MASONRY CONSTRUCTION. By IRA 0. BAKER, C. E. Materials— Methods of Using Materials— Foundations- Masonry Structures— Etc., Etc. Illustrated with numerous cuts and six folding plates. 8vo. Cloth, $S'00. for sale by THE ENGINEERING NEWS PUBLISHING COMPANY, Tribune Building, New York. ROAD LEGISLATION FOR THE AMERICAN STATE, • By J. W. JENKS, Ph.D., Knox College, Galesburg, III. 7 5 C K JSr T S . FOR SALE BY ENGINEERING NEWS PUBLISHING CO, Trinidad Asphalt Sheet Pavements AEE IN USE IN Albany, Harrisburg, St, Paul, Buffalo, Kansas City, St. Louis, Brooklyn, Louisville, St. Joseph, Baltimore, Montreal, Syracuse, Binghamton, New York, Topeka, Boston, Newark, Toledo, Cincinnati, New Orleans, Toronto, Chattanooga, Omaha, Utica, Columbus, Philadelphia, Washington, Chicago, Rochester, Wilkesbarre, Detroit, Savannah, Wichita, Erie, Schenectady, Wyandotte, Ft. Wayne, Scranton, Youngstown, TO THE EXTENT OF OVER 5 MILLION SQ. YARDS, And in each City there is an Urgent Dennand for More of It. This Pavement is laid with GENUINE TRINIDAD ASPHALT, without ad- nnixture of Coal Tar or any of its products. It GREATLY ENHANCES the VALUE OF REAL ESTATE, and has MORE POINTS OF MERIT AND FEWER DEFECTS THAN ANY OTHER PAVEMENT. DURABILITY GUARANTEED. For infornnation and estinnates apply to Warreii-Scliarf Asjlalt Pa?ii Co, 81 FULTON ST., NEW YORK.