..^i^PPlPii91S5ilii3ii!li31'f'l!f'''iSWi^^ 
 
 AN 
 
 ESSAY 
 
 ON THE CONSTRUCTION Of 
 
 WHEEL-OARRIAGES, 
 
 AS THEY AFFECT BOTH 
 
 ROADS AND HORSES; 
 
 WITH SUGGESTIONS RELAXING TO 
 
 TOLLS 
 
 AND THE 
 
 FORMATION OF ROADS. 
 
^6 /3 A i 
 
 ::> 
 
 
 ^yjl^^^X/- ^ 7</<:^-.^.^^^ S'S 
 
AN 
 
 ESSAY 
 
 ON THE CONSTRUCTION OF 
 
 WHEEL-CARRIAGES, 
 
 AS THEY AFFECT BOTH 
 
 THE RO.\DS AND THE HORSES ; 
 
 WITH 
 
 SUGGESTIONS 
 
 RELATING TO THE PRINCIPLES ON WHICH 
 
 TOLLS 
 
 OUGHT TO BE i:\IPOSED, 
 
 AND 
 
 A FEW REMARKS ON THE 
 
 FORMATION OF ROADS. 
 
 JOSEPH STORRS FRY 
 
 iLonli0n: 
 
 PRINTED FOR 
 
 J. AND A. ARCH, CORXHILL; BALDWIN AND CO. PATERNOSTFK- 
 
 ROW, AND HARDING, ST. JAMES's STREET; 
 
 AND T. J. MANCHEE, BRISTOL. 
 
 1820. 
 
Printed by T. J, Manchee, Bristol. 
 
The greatest part of the following 
 Essay was written in the winter 1 798 - 9. 
 ^ince which time several valuable commu- 
 ideations have been made to the Public, on 
 the subject of Wheel-Carriages. Still, how- 
 ever, the Author of these pages conceives 
 that there are some important considerations, 
 connected with this subject, that have never 
 been noticed by any other writer ; otherwise 
 his manuscript would have remained on the 
 shelf. But considering that it is a duty we 
 owe to Society, to endeavour to add to the 
 stock of useful information, he has presumed 
 to submit his thoughts to the Public ; and 
 he hopes they will meet with candid and 
 impartial investigation from those by whom 
 they may be perused. 
 
VI 
 
 The Author deems it proper to add 
 thaty as it is his ivish to render this work 
 an object of interest to persons not conver- 
 sant with such subjects, he has studiously 
 avoided technical phrases, as well as those 
 that are not in frequent use ; hut, when such 
 necessarily occur, they are generally accom- 
 panied icith an explanation : on this account, 
 his style may be censured as too familiar; a 
 charge he very willingly risks, for the sake 
 of obtaining what ought to be the great 
 object of every Writer, that of being under- 
 stood by his Readers ; and how far he has 
 succeeded they ivill judge. 
 
 Frenchay, near Bi isto), 
 6th Mouth 21, 1820. 
 
CONTENTS. 
 
 CHAPTER I. 
 
 1. On the Mechanical Use of Wheels, in lessening Fric- 
 tion. — 2. Polished Axles in Oil cause very little resistance to 
 the Horses. — 3. Objects which are the principal Causes of 
 Resistance to the labour of the Horses. — 4. Axle-friction, in 
 some cases very great. — 5. Wheels act as Levers in sur- 
 mounting obstacles ; demonstrated. — 6. High Wheels ad- 
 vantageous, only to a certain extent. — 7. Table of Powers 
 equal to the Resistance of Wheels, when opposed to certain 
 objects. — 8. Power is actually exerted in surmounting an 
 obstacle, as set down in the Table, notwithstanding the 
 velocity or momentum that any Carriage may have acquired. 
 
 CHAPTER n. 
 
 1. Conical Wheels injurious, both to Roads and Horses. 
 ' — 2. Conical Wheels wear out faster than Cylindrical ones. 
 — 3. Cylindrical Wheels and Axles best. Subject to only 
 three-fourths the usual Toll. — 4. High Wheels not disad- 
 vantageous going up hill. — 5. Broad- Wheel Waggons ex- 
 tremely injurious to the Roads. Projecting-heads of Tire- 
 Nails. — 6. Broad-Wheel Waggons not so advantageous to 
 the Public Carrier as lighter Carriages. 
 
VI CONTENTS. 
 
 CHAPTER III. 
 
 1. Modern Stage-Coaches ; unphilosophical. Supposed 
 origin of the custom of persons riding on the tops of them. 
 — ^. Regulations for the security of Passengers suggested. 
 — 3. All Passengers by Public Carriages might be, and 
 ought to be, protected from the weather. — 4. Objections 
 answered. Traces of Horses drawing, ought to be placed 
 horizontally. By the presertt construction of Coaches, 
 Horses have to draw the same load, over the same obstruc- 
 tion, twice. — 5. Centre of gravity of these Coaches simply 
 illustrated. 
 
 CHAPTER IV. 
 
 1. A new principle suggested, as important in the Con- 
 struction of Carriages, viz. the Division of Weight, or 
 Power, by the use of a greater number of Wheels for the 
 same load ; thus causing less labour to the Horses and less 
 injury to the Roads. — 2. Carriages should press the road 
 with the least possible weight on any one wheel. Less 
 labour required to draw several wheels in succession, over 
 an obstruction, than to draw one wheel, carrying the same 
 amount of weight, over the same object. — 3, 4, 5. Illustra- 
 tion of this Theory. — 6. Breadth of wheels no security 
 against the destructive effects of pressure. Broad Wheels 
 on paving-stones. — 7- The principle of light pressure should 
 be carried as far as may be consistent with public conve- 
 nience. — 8. Light Waggons for one horse suggested. — 
 9. Six-wheel and Eight-wheel Carriages recommended. 
 Were in use some years ago. Were remarkably easy to 
 travellers. — 10. Had one defect in construction. — 11. Carried 
 enormous loads with four horses. 
 
 CHAPTER V. 
 
 1. Friction docs not increase with the increase of the 
 rubbing-surfaces: proved; consequently not with an in- 
 
CONTENTS. Vll 
 
 crease of the number of axles. Practice of the Author.— 
 2. Practical use of many wheels. — 3. Proposed remedy for 
 the old defect in the construction of Six-wheel and Eight- 
 wheel Carriages, illustrated by engravings. — 4. Causes why 
 the Six-wheel and Eight-wheel Coaches were discontinued. 
 ■: — 5. Suggestions for obviating these causes. — 6. Matthews's 
 Patent Coach. 
 
 CHAPTER VI. 
 
 1. Comparative effect on the Horses, by the use of Car- 
 riages of Two wheels, of Four wheels, of Six wheels, and 
 of Eight wheels, all carrying the same gross weight. Illus- 
 trated by a Table. — 2. Fore-wheels the pioneers of the hin- 
 der-wheels. — 3. The roads doubly interested in the question 
 of heavy or light pressure. 
 
 CHAPTER VII. 
 
 1, Tolls should be imposed on Wheels only, without re- 
 gard to the number of horses drawing any carriage. — 2. A 
 liberal number of horses, to any carriage, advantageous to 
 the Road. — 3. Eight- Wheel Carriages, to weigh forty-eight 
 bundred-weigiit gross, ought to be encouraged by low tolls, 
 as most advantageous to the Proprietors, and to the Roads. 
 4. If intensity of pressure on each wheel be removed, the 
 form or width of the wheel is of little consequence. — 5. 
 Cylindrical wheels preferable, even for the lightest weights. 
 
 CHAPTER VIII. 
 
 1. Principle onwliich Tolls ought to be imposed. — 2. How 
 a Table of Tolls ought to be calculated, to meet this prin- 
 ciple. — 3. A Table of Tolls, calculated on this principle. — 
 4. Operation of Tolls so calculated. Opinion of John 
 Loudon M'Adam. — .5. Opinion of the Legislature, in I3th 
 Geo, HI. on the injury caused by excessive weights. Sixteen- 
 
Vlll CONTENTS. 
 
 inch rollers, as now constructed, liable to an additional toll 
 of Forty Pounds. — 6. Breadth of Wheels no security against 
 the destructive effects of pressure, further shewn. — 7- Proba- 
 ble reasons why Heavy Waggons were formerly encouraged, 
 — 8. Wheels of light pressure more urgently necessary, 
 where the materials for roads are of a soft and bad 
 quality. 
 
 CHAPTER IX. 
 
 1. Springs, their use explained. How they operate to the 
 ease of the Rider. — Richard Lovell Edgewobth's Expe- 
 riments on Springs. 
 
 CHAPTER X. 
 
 1. Suggestions respecting the Tax on Stage-Coaches. — 
 
 2. Private Carriages. Taxed Carts. 
 
 CHAPTER XT. 
 
 1. Mechanical Action of Wheels on the Materials of 
 Roads explained. — Q. Narrow Roads, why so frequently in 
 bad condition. Deep ditches and sudden falls of the 
 ground, close to the sides of roads, productive of ruts. — 
 
 3. Convex Roads never wear well, and why. — 4. Materials 
 for Roads. Laying on of Materials. — 5. Whether a thick or 
 a thin covering at one time. — 6. Whether the whole breadth 
 of a road, or only half of it, should be covered at one time. 
 
 APPENDIX. 
 
 Remarks on the Friction of Axles, the Elasticity of the 
 Subsoils, and the Softness of the Surface-matte; of Roads, 
 as relating to the principle of Division of v^oight.— Ou 
 Fat and Oils of different kinds, as applicable to the Axle? 
 of Wheels, and to other Machinery. 
 
ESSAY, 
 
 &c. 
 
 CHAPTER I. 
 
 1 • On the Mechanical Use of Wheels, in lessen- 
 ing Friction. — 2. Polished Axles in Oil cause 
 very little resistance to the Horses. — 3. Objects 
 which are the principal Causes of Resistance 
 to the labour of the Horses. — 4, Axle -friction ^ 
 in some cases, very great. — 5. Wheels act as 
 Levers in surmounting obstacles ; demonstra- 
 ted.— Q. High Wheels advantageous, only to 
 a certain extent. — 7. Table of Powers equal 
 to the Resistance of Wheels, when opposed to 
 certain objects. — 8. Power is actually exerted 
 in surmounting an obstacle, as set down in the 
 Table, notwithstanding the velocity or mo- 
 mentum that any Carriage may have acquired. 
 
 1 . 1 HE use of wheels, in lessening friction, 
 is well defined, in an Essay published in the 
 year 1790, by my friend Robert Anstice, 
 of Bridgewater. He says, " A Carriage, 
 
 B 
 
2 ESSAY ON [chap. I. 
 
 such as a sledge, sliding over a plane (or 
 road), sujfifers a friction, or rubbing of its 
 parts against the plane, equal to the distance 
 through which it moves ; but, if an axle 
 be applied to it, whose circumference shall 
 be six inches, and on that wheels be placed, 
 whose circumference shall be eighteen feet, 
 it is evident that, in moving the carriage 
 eighteen feet over the plane, the wheels 
 will make but one revolution ; and as there 
 is no sliding of parts between the plane 
 and the wheels, but a mere change of sur- 
 face, by one part of the latter rising, and 
 the other descending, nearly perpendicular 
 to the former, no friction will take place 
 there ; the whole being transferred to the 
 nave acting on the axle ; which nave^ having 
 made but the same one revolution as the 
 outer circumference of the wheel, there has 
 been but a sliding of parts equal to the cir- 
 cumference of the hole in the nave; which, 
 if it fitted the axle, would be but six inches. 
 Consequently, the friction is lessened as one 
 to thirty-six, besides the advantage gained 
 
CHAP. I.] WHEEL-CARRIAGES. 3 
 
 of confining it to so small a surface, whereby 
 the parts are more easily kept smooth, and 
 fitted to each other ; and substances (oil or 
 grease) applied and retained to lessen the 
 remaining friction." — Indeed the difference 
 between drawing a sledge eighteen feet, or 
 even fifteen feet, upon a rough road, and 
 drawing the same weight supported by 
 polished steel, sliding upon polished brass, 
 with olive-oil between them, six or even 
 nine inches, is astonishingly great. 
 
 2. In the latter case, the friction is so 
 wonderfully reduced as to be scarcely an 
 object of consideration. In what degree it 
 is reduced it would be difficult to determine, 
 even by experiment ; as the friction of sledges 
 varies on every variety of road : it is also 
 different in wet weather and in dry. I do 
 not, however, think that more than one 
 hundredth part of the labour of the horses is 
 expended, in overcoming the friction of these 
 polished oiled metals one against another. 
 I insist the more on this point, as it is im- 
 
 b2 
 
4 ESSAY ON [chap. I. 
 
 portant to know what causes the resistance 
 which our horses have to overcome, and 
 because I think that the friction of the axles 
 is very much over-rated. That it is very 
 highly rated is evident, by the wonderful 
 effects that are announced, as produced by 
 Such and such Patent Boxes ; as though 
 the labour of the horses were to be reduced 
 in a very considerable degree by the use of 
 them. Those axles and boxes are undoubt- 
 edly the best, of which the axles are polished 
 steel, and perfectly cylindrical ; and the 
 boxes, brass, neatly bored, and all well fitted 
 together, with the least shoulder-friction'^ 
 and furnished with a reservoir for oil. 
 
 3. The other ninety-nine hundredths of the 
 power are applied in overcoming all the ob- 
 jects which cause resistance under ordinary 
 circumstances ; which would not exist, if the 
 outward edges of the wheels were of steel, 
 accurately turned in lathes ; and if the car- 
 riages moved on surfaces of polished steel, 
 perfectly horizontal ; and if all resistance 
 
CHAP. I.] WHEEL-CARRIAGES. 5 
 
 from the atmosphere were removed. These 
 objects consist of, — First, the greater ine- 
 qiiahties of the roads, which we call hills. 
 Secondly, the lesser inequahties which every- 
 where present themselves ; for even the best 
 roads are not mathematical planes, but a 
 succession of little risings and fallings. 
 Thirdly, the resistance occasioned by the 
 pressure of the wheels into the surface of the 
 road ; which is generally something, more 
 or less, according as the road is more or less 
 hard or soft, and more or less clean or dirty ; 
 which is commonly a cause of prodigious 
 expenditure of the strength of the horses. 
 Soft materials, dirt, dust, and sand, operate 
 as a perpetual Iiill against the wheels. I 
 have known a horse with a gig more fatigued 
 by going a few miles on a firm sand sea- 
 beach, when the wheels did not sink more 
 than half an inch, than he would have been 
 by going three times the distance on a hard 
 road. The fourth cause of resistance is the 
 air; which, to lofty coaches, covered with 
 outside-passengers and luggage, is often very 
 
6 ESSAY ON [chap. I. 
 
 great ; particularly when they meet a strong 
 wind. It frequently happens that when a 
 coach is travelling at the rate of nine miles 
 an hour, it is opposed by a wind going as 
 fast ; which forms a resistance equal to a 
 wind going eighteen miles per hour. There- 
 fore carriages should be so constructed as 
 to meet with as little resistance of this kind 
 as possible. 
 
 4. It were however absurd to speak of 
 axle-friction in general terms. I have ven- 
 tured an opinion that, in case of polished 
 axles and brass boxes, with fine oil between 
 them, which should be pure olive-oil, una- 
 dulterated with rape-oil, which is of a vis- 
 cous, glutinous quality, — axle-friction is not 
 more than equal to one hundredth part of the 
 power of the horses. But, in the case of 
 clumsy wooden axles, smeared over with a 
 composition of tar and cow-dung, the friction 
 may be so considerable as to neutralize a 
 fifth, a fourth, or even more, of the strength 
 of the horses ; and so in proportion, as axles 
 
CHAP. I.] WHEEL-CARRIAGES. 7 
 
 are well or badly constructed. And as the 
 substance interposed may be of a hibncous, 
 or of a viscous and tenacious quality, th3 
 axle-friction will be less or greater — or, in 
 other words, in that proportion the wheels 
 will turn round with ease or with difficulty. 
 
 5. The action of a wheel as a lever, in 
 overcoming an obstacle, may be demoi^i- 
 strated by the following* diagram. 
 
 The circle represents a wheel 6 feet in 
 
8 ESSAY ON [chap. I. 
 
 diameter — C being- the centre ; O an obsta- 
 cle 3 inches iiigh ; G the ground ; T C 
 the hne of draft or traction. The lever is 
 represented by the lines C O and O G ; of 
 which C O is the arm of the lever ; and O G 
 the opposite or lifting end ; O being the ful- 
 crum on vv^hich the lever turns. In order, 
 hovs^ever, to ascertain the power of this lever, 
 we must reduce each member of it to right 
 angles with the lines of their respective direc- 
 tions. This will give us the line D O, at 
 right angles with the line of traction, and 
 the line O B, at right angles with the line in 
 the direction of which the weight is to be 
 lifted. Now, the power required to be ap- 
 plied to the line T, to balance 100 pounds at 
 the end of the lever at B, is inversely as the 
 length of the line U O is to that of O B. 
 The length of the line D O is equal to one half 
 the diameter of the wheel, minus the height 
 of the obstacle, or 33 inches. The line O B, 
 being the mean proportional between the two 
 lines A B, which is 69 inches long, and B G, 
 which is 3 inches long, is 14*3875 inches 
 
CHAP. I.] WHEEL-CARRIAGES. 9 
 
 long. (Euclid, B. VI. 13.) The question, 
 then, may be stated thus : 
 
 Inches. Inches. Pouuds. Pounds. 
 
 As SS : 143875 : : 100 : 43 o89, 
 or little more than 43 pounds and a half; 
 which is the power, or weight, falling over 
 a single pulley, drawing in the direction T, 
 necessary to balance 100 pounds, on a wheel 
 6 feet high, when opposed by a stone, or 
 other obstruction, 3 inches high. 
 
 It will be obvious that, as the wheel rises 
 over the stone, the line O D must gradually 
 lengthen ; and the line O B nmst gradually 
 shorten : consequently the resistance occa- 
 sioned by the stone gradually decreases, until 
 C rises perpendicular to O ; when it entirely 
 ceases. 
 
 6. It is shown, above, that a wheel is really 
 a mechanical power, operating as a lever ; 
 and this philosophical advantage increases 
 with the increased size of the wheel. But 
 this advantage is more than counterbalanced 
 by a disadvantage, which, after a certain 
 
10 ESSAY ON [chap. I. 
 
 period, increases in a much greater ratio 
 than the advantage ; which is the weight of 
 the wheel itself. Because, to make a cart- 
 wheel 10 feet high, it would be necessary to 
 have the spokes not merely twice as long as 
 for a 5-feet wheel, but they must be twice or 
 thrice the substance, consequently four or six 
 times as heavy ; there must also be more of 
 them. The stock or nave must also be much 
 heavier ; the axle much stronger ; and the 
 fellies, as well as the tire-iron, must be both 
 much stronger and twice the circumference : 
 therefore such a pair of wheels, with the axle, 
 would be a load of themselves. In order to 
 convey a tolerably correct idea on this subject, 
 I have calculated what weights, falling over 
 a single pulley, would be equal to the resist- 
 ance which wheels of different heights, car- 
 rying 100 pounds gross weight each, would 
 occasion, when opposed by an obstruction 
 3 inches high ; and also by an obstruction of 
 1^ inch high; the wheel, in each case, being 
 supposed to be in a state of rest. 
 
CHAP. I.] WHEEL-CARRIAGES. 11 
 
 7. An obstruction 3 inches high would 
 cause resistance to wheels carrying 100 
 pounds gross each, as follows, viz. 
 
 To a wheel 6 feet, inches, equal to 43| pounds. 
 
 5 — 8— 45 — 
 
 5 — 4 — 46| — 
 
 5 — — 481 -- 
 
 4 — 8 — 50| — 
 
 4 — 4 — 52i — 
 
 4 — 0— 55 — 
 
 3 — 8— 58 — 
 
 3 — 4— 62 — 
 
 3 — 0— 66 — 
 
 2 — 8 — 7H — 
 
 :i — 4 — 78i — 
 
 2 — 0— 88 — 
 
 An obstruction, l^ inch high, would cause 
 resistance to wheels carrying 100 pounds 
 gross each, as follows, viz. 
 
 To a wheel 6 feet, inches, equal to 30 pounds. 
 
 5 — 8 — 3of — 
 
 5 — 4 — 31i — 
 
 5 — — 32| — 
 
 4 — 8— 34 — 
 
 4 — 4 — 35| -^ 
 
12 ESSAY ON [chap. I. 
 
 To a wheel 4 feet, inches, equal to 37 pounds. 
 
 3 — 8 ~ 3!) — 
 
 3 — 4 — 41 — 
 
 3 — — 43i — 
 
 2 — 8 — 461 — 
 
 2 — 4 — 50i — 
 
 2 — 0— 55 — 
 
 My object being to make these remarks 
 as plain as possible, I have thought it best 
 in these Tables to omit decimal fractions. 
 The result of both evidently is, that the 
 small advantage gained from the use of 
 wheels above 4 feet 6 inches high, would 
 not compensa'e for the inconvenience and 
 increased weight of higher wheels. 
 
 It is also evident, from the latter Table, 
 that the disadvantage of using small wheels 
 does not increase so rapidly as in the former 
 Table. 
 
 Another circumstance also is to be ob- 
 served in these Tables as important, — that, 
 in the latter Table, wheels require exactly 
 the same power as those of twice the height 
 in the former Table, or in exact proportion 
 
CHAP. I.] WHEEL-CARRIAGES. 13 
 
 as the obstruction is reduced. Hence the 
 necessity of making our roads as smooth and 
 as hard as possible. 
 
 8. It may be here proper to meet an ob- 
 jection that may possibly be raised, respecting 
 the power which I have stated as necessary 
 to carry a wheel over an obstruction. It 
 may be said that tlie velocity, or momentum, 
 which a coach may have acquired, is suffi- 
 cient to carry the wheel over the object. Be 
 it so. But the coach does, by going over 
 this object, lose just as much of its momen- 
 tum as is equal to the power necessary to 
 carry the wheel over the object from a state 
 of rest; and the horses nmst exert exactly 
 so much additional power, to keep up, or 
 recover, the speed of the coach, before their 
 traces will be as slack as they previously 
 w^ere. 
 
15 
 
 CHAPTER II. 
 
 1 . Conical Wheels injurious, both to Roads and 
 Horses. — 2. Conical Wheels wear out faster 
 than Cylindrical ones. — 3. Cylindrical Wheels 
 and Axles best. Subject to only three-fourths 
 the usual Toll. — 4. High Wheels not disad- 
 vantageous going up-hill. — 5. Broad Wheel 
 Waggons extremely injurious to the Roads. 
 Projecting -heads of Tire-Nails. — 6. Broad- 
 Wheel Waggons not so advantageous to the 
 Public Carrier as lighter Carriages. 
 
 1. I KNOW no prejudice more firmly rooled 
 than that in favour of dishing or conical 
 wheels. Much has been written, and well 
 written, to show, and to prove, the absurdity 
 of tlie use of them, but hitherto with very 
 little effect. I think the principles, and the 
 effects of them, may be stated in very few 
 words. 
 
16 ESSAY ON [chap. II. 
 
 Carriages are intended to travel straight 
 forward : they ought, therefore, to be fur- 
 nished with wheels, the natural tendency of 
 which should be to go straight forward. 
 The same with a garden-roller : suppose any 
 man were to have a garden or a field-roller, 
 made six inches less in diameter at one end 
 than at the other ; what would not even the 
 wheel- Wrights say of such a man ? Yet such 
 an act would be a counterpart of their own, 
 when they recommend broad conical wheels. 
 The natural course of a rolling cylinder is a 
 straight line ; and the natural course of a 
 rolling cone is a circle. Let us reverse their 
 natural courses : that is, let us make a cylin- 
 der travel in a circle, and a cone in a 
 straight line. It must be obvious that, when 
 each of these bodies is forced to travel con- 
 trary to nature, in the course of the other, 
 there must be a constant dragging, or twist , 
 on the ground, to keep it in its unnatural 
 course. Such would be the case if a man 
 were to drag a common garden-roller round 
 in a small circle ; and such, too, would be 
 
CHAP. II.] WHEEL-CARRIAGES. 17 
 
 the case, if a man were to draw straight for- 
 ward a garden-roller made six inclies less in 
 diameter at one end than at the other. The 
 effect in both cases would be, precisely^ the 
 same. Each operation would be attended 
 with prodigious labour; and the roller, in 
 each case, by its twist on the ground, would 
 break up and derange the gravel beneath. 
 Now it is well known that the machine con- 
 stantly in use, in numberless manufactories, 
 as the best that has hitherto been invented 
 for expeditiously and effectually grinding to 
 powder the hardest and toughest materia-^, is 
 a cylinder forced round in a circle. There- 
 fore, as a cylinder moving in a circle is the 
 best machine that the ingenuity of man has 
 hitherto produced for pulverizing the haraest 
 and toughest materials, and as this is effected 
 by the twist or drag produced between the 
 edge of the cylinder and the surface on 
 which it rolls, and as the twist or dra^ is 
 precisely the same in the case of a C(»ne 
 forced straight forward, I think I may be 
 borne out in my opinion that a heavy wag- 
 
 e 
 
18, ESSAY ON [chap. II. 
 
 gon, with broad comical wheels, is the most 
 con^piete, the most efficacious machine that 
 the art of man, in the present state of 
 science, could construct, for grinding to 
 powder the materials of our roads.* 
 
 2. And it is also true that, as the wheel 
 grinds the road, in that proportion does the 
 road grind the wheel. The tire of cylindri- 
 cal wheels, therefore, would last probably 
 many times as long as that of conical 
 wheels. 
 
 3. It appearing, then, that the cylindrical 
 wheel only has a natural tendency to roll 
 straight forward, all carriage-wheels ought 
 to be so constructed. Consequently the ends 
 of the axles ought not to be conical or 
 tapered, nor bent down, as they are now 
 
 * On looking over the Essay on Wheel-Carriages, pub- 
 lished in the year 1813, by Richard Lovell Edgeworth, 
 I find the same comparison in illustration of the ettects 
 of Broad Conical Wheels. But as the above is copied 
 from my own manuscript, written twenty years ago, I 
 hope not to incur the charge of plagiarism. 
 
CHAP. II.] WHEEL-CARRIAGES. 19 
 
 made ; but the axle ought to be put into a 
 lathe, and both ends turned, like the two 
 ends of a spindle for mill-work, cylindrical ; 
 that is to say, of the same size or diameter 
 at the ends as they are at the shoulders; 
 and, of course, the boxes in the wheels 
 should be cylindrical also. 
 
 It should be known that wheels of .this 
 construction are liable to only three-fourths 
 of the usual toll, by the 55lh Geo. III. 
 chap. 119, at the discretion of the Trustees. 
 
 4. It is a general notion that high wheels 
 act disadvantageously, going up-hill. That 
 this is not the fact, is demonstrated by the 
 ingenious Author before cited. He says, 
 " Wheels, when ascending inclined planes, 
 and when the line of traction is kept parallel 
 to their ascent, notwithstanding they act as 
 levers ; yet, in this case, the action of the 
 weight will increase with that of the power 
 gained by the increased size of the wheel ; 
 which size, therefore, will be of no other 
 consequence than, by lessening the friction, 
 
 c 2 
 
20 ESSAY ON [chap. II. 
 
 as it does in wheels passing over planes."* 
 It seems the Author is showing that high 
 wheels possess no philosophical advantage 
 over lower ones, in ascending hills, other than 
 they have on level ground ; but he also shows 
 that neither have they any disadvantage. 
 
 5. It being shown, above, that the conical 
 wheels of Broad- wheel Waggons are the 
 same, in operation and effect, on the mate- 
 rials of the roads, as Drug-mills, it follows, 
 of course, that all that portion of labour 
 which is applied to the conical wheel, to 
 keep it in a straight course, more than would 
 be required to impel it in its natural circle, 
 is so much power, not merely wasted, but 
 most mischievously and most effectively ap- 
 plied in grinding the materials of the road 
 into powder ; and as these waggons weigh, 
 in summer, Eigl^t Tons each, the silent 
 mischief effected by these four drug-mills of 
 Two Tons weight each, is great beyond 
 
 " Anstlce on Wheel-Carriages, p. 32. 
 
CHAP. II.] WHEEL-CARRIAGES. 21 
 
 calculation. How much power is thus mis- 
 applied may be conceived, as it frequently 
 requires ten of the heaviest horses to draw 
 it; which is just sixteen hundred-weight 
 each — a weight sometimes drawn by light 
 horses, in stage-coaches, and at least at 
 three times the pace! 
 
 Lest a total silence on the subject of pro- 
 jecting-heads to the Nails of wheels might 
 be construed into an approval of their use, 
 I am induced to make a remark or two upon 
 them. — First, the effect of round projecting- 
 heads, when the carriage is heavily loaded, 
 the weight of the wheel with its load pressing 
 only on a point, is, that inevitable destruction 
 must ensue to the stone with which it hap- 
 pens to come in contract, even though such 
 stone were firmly imbedded in the road. 
 And, secondly, as they affect the horses, it 
 is demonstrable that they are extremely in- 
 jurious ; because, in this point of view, it 
 matters not whether these round knobs of 
 iron be affixed to the wheels, or whether 
 the wheels be smooth, and these knobs of 
 
22 ESSAY ON [chap. II. 
 
 iron laid in the path of the wheels. Now, 
 surely even the most inexperienced Carter, 
 were he driving a waggon with smooth 
 wheels, and seeing such knobs of iron strewed 
 along the road in two tracks, would endea- 
 vour to avoid them, well knowing that his 
 horses would draw their load more easily 
 on any other part of the road. But these 
 large heads are of no use whatever to the 
 wheels ; because, if the nails be properly 
 countersunk, and the heads made exactly 
 alike, for which purpose they should be 
 made in a mould, and so adjusted to the 
 hole in the tire as to hold fast at the bottom 
 of the hole, the tire-iron will remain firm 
 until it is reduced to the thickness of a penny- 
 piece ; whereas, if the nails hold only at 
 the top, as this wears away, the tire of 
 course soon becomes loose. Therefore, as 
 projecting-heads to tire-nails are extremely 
 injurious to the roads, and in a very great 
 degree productive of increased labour to 
 the horses, and as they are in evei'y 
 other point of view entirely useless, they 
 
CHAP. II.] WHEEL-CARRIAGES. 23 
 
 ought, I think, to be absolutely prohibited 
 by Act of Parliament. 
 
 6. It is a happy coincidence that, fi'e- 
 quently, what tends to private advantage 
 tends also to the advantage of the public. 
 I am glad to see these Gothic vehicles, which 
 are objects of terror to the traveller, and 
 which are destructive in the highest degree 
 to the roads, gradually giving way to light 
 carriages, drawn by four horses, and driven, 
 as coaches are, by a man on the box. The 
 owners have discovered the secret that horses 
 in these carriages can draw nearly as much 
 weight, five or six miles per hour, as other 
 horses, nearly twice as heavy, can draw in 
 heavy waggons, about two miles per hour. 
 
 Admitting the truth of the preceding 
 statement respecting heavy waggons, it 
 follows that, instead of being encouraged, as 
 they now are, by low tolls, and in some 
 cases by an entire exeniption from toll, they 
 ought to be subjected to a toll that would 
 soon effect their extinction. 
 
25 
 
 " Licensed to carry Six Inside and Twelve Otttside." 
 
 CHAPTER III. 
 
 1. Modern Stage -Coaches ; unphilosophical. 
 Supposed origin of the custom of persons 
 riding on the tops of them. — 2. Regulations 
 for the security of Passengers suggested. 
 — 3. All Passengers hy Public Carriages 
 might he, and ought to he, protected from the 
 weather. — 4. Ohjections answered. Traces of 
 Hordes drawing ought to heplaced horizontally. 
 By the present construction of Coaches, Horses 
 have to draw the same load, over the same oh- 
 struction, twice. — 5. Centre of gravity of these 
 Coaches simply illustrated. 
 
 1. In the construction and use of stage- 
 coaches, notwithstanding the display of paint 
 and varnishj I think there is less display of 
 
116 
 
 ESSAY ON 
 
 [chap. III. 
 
 any thing like science, or even common sense 
 than in most things about us. I have often 
 questioned, whence the absurd custom of 
 persons riding on the tops of coaches, over 
 the heads of one another: and the sohition 
 is this : when coaches were first built, the top 
 was considerably convex ; a form which 
 naturally presented itself to the builder, to 
 turn off the rain ; as appears by the annexed 
 representation of a coach of about the 
 middle of the last century. 
 
 This was undoubtedly the use and the sole 
 use of that part of the carriage, most likely 
 for a century after it was first invented. But 
 it was, in my opinion, no more contemplated, 
 by the early builders of coaches, that men 
 should ride on the tops of them, than it now 
 is that they should ride on the tops of sedan- 
 chairs. The one is just as reasonable, just 
 
CHAP. III.] WHEEL-CARRIAGES. 27 
 
 as unreasonable and absurd, as the other. I 
 have no {\oubt but that the custom originated 
 thus : A coachman, driving along, overtakes 
 a poor fellow on the road. — Coachman ! can 
 you give me a lift ? — No. I'm quite full ; 
 and I've no room on the box. — Oh ! let me 
 get up ; I can ride on the toj) of the coach.-^ 
 The poor traveller mounts aloft, and holds 
 on as far as he is going ; and the coach- 
 man gets his SHILLING. This is the secret 
 Next time the coachman takes up two ; and, 
 after a little time, the thing attracts the notice 
 of the master, who perchance may like shil- 
 lings as well as his man. Then follow 
 arrangements for outside-passengers : first 
 the foot-board behind the boot, to support 
 the feet, and to prevent people from falling 
 through between the boot and the body of 
 the coach ; then the bridle, a strap of leather, 
 one end fastened to one side, and the other 
 end fastened to the other side of coachman's 
 box, long enough for the outside-passengers 
 to hold themselves on by it. All this I well 
 remember. Then followed the side-irons.; 
 
28 ESSAY ON [chap. III. 
 
 then similar arrangements at the back-part 
 of the coach ; and, lastly, the dickey-seat ; 
 and all this for the sake of the shillings — 
 all an innovation, thus accidentally intro- 
 duced, contrary to the use for which coaches 
 were first made — sanctioned and regulated, 
 too, by the sage authority of the British 
 Legislature ; who have decreed that only 
 twelve persons besides the coachman, and 
 perhaps half a ton of luggage, shall be thus 
 mounted aloft — all in defiance of every prin- 
 ciple of sound philosophy and common 
 sense, and at the peril of the life of every 
 traveller, inside or outside, who goes by 
 these coaches. A gross reflection on the 
 wisdom of the Legislature, and on the good 
 sense of the Nation ! 
 
 2. I would propose a very concise Act of 
 Parliament, for' the regulation of these 
 coaches, to consist only of two clauses. 
 
 First. That no passenger shall be allowed 
 to sit on any seat, cushion, luggage, or other 
 thing, higher than five feet from the ground ; 
 
CHAP. III.] WHEEL-CARRIAGES. 29 
 
 excepting only one person on the box with 
 the coachman. 
 
 Secondly. That neither the roof of the 
 coach, nor any luggage, nor any other thing, 
 belonging to or about the coach, excepting 
 only the coachman, and one person sitting 
 by him, shall, on any account whatsoever, 
 exceed eight feet four inches from the 
 ground. 
 
 3. These two enactments would be suffi- 
 cient for the public security ; and ample 
 scope would be left for the exercise of skill. 
 If it be necessary to carry a large number of 
 persons in one vehicle, they may be accom- 
 modated by a series of cross-seats, one 
 behind another ; which may be divided into 
 compartments, for passengers of different 
 degrees, and another compartment for lug- 
 gage. And every person who travels ought 
 to be protected from the weather. There can 
 be no question but that many a poor traveller, 
 who has not a second coat to his back, re- 
 ceives what may be called his death-warrant, 
 
30 ESSAY ON [chap. III. 
 
 when exposed, for a winter's night, to frost 
 and snow, on one of these coaches. The 
 poor ought to be sheltered as well as the 
 rich. The whole of our coach-system is 
 unphilosophical and barbarous — unworthy of 
 such an enlightened country as England.* 
 
 4. Here it may be objected that the con- 
 sequence of lengthening the carriage and 
 lowering the load will be, that the weight 
 would follow more heavily after the horses. 
 It would certainly be difficult to satisfy such 
 objectors, who would be likely to be of the 
 class called Men of Experience, that is to 
 say, men brought up in a routine of practice, 
 yet totally ignorant of principles. It seems as 
 though they had a notion that the fore-wheel 
 
 * " It appears by the Newspapers that on the night 
 of Tuesday the 25th of February, 1812, three outside- 
 passengers were found dead on the roof of the Bath 
 coach, from the inclemency of the weather. Neither 
 money nor time is gained by exposing females and sickly 
 people on the tops of coaches, in snow and rain, and to 
 the hazard of their lives. " — Edgeworth on fVheeU 
 Carnages, p. 146. 
 
CHAP. III.] WHEEL-CARRIAGES. 51 
 
 of a carriage, when closely followed by the 
 hind-wheel, makes haste out of its way ; as a 
 little boy at school, when pursued by a bigger 
 boy, runs as fast as he can, for fear of being 
 tripped up. All these notions about the ne- 
 cessity of horses being close to their work, 
 and of wheels following as nearly as possible 
 after each other, and of coaches that are 
 loaded high running lighter than when the 
 load is low, are completely refuted by the 
 actvial experiments of Richard Lovell Edge- 
 worth. See his work. 
 
 It is very true that if the wheel-horses 
 draw upivard, by having the traces fixed to 
 the carriage lower than the points at which 
 they are attached to the hames, they have a 
 firmer hold on the ground than they other- 
 wise would have ; but in such a case the 
 horses lift a part of the load, and what 
 they lift they carry ; and what they thus 
 carry, they carry on their neck or shoidders, 
 I have known an instance of a man, who 
 could not get his horse and cart up the ascent 
 of a bridge, who, after much persuasion 
 
32 ESSAY ON [chap. III. 
 
 from a by-stander, was induced to get upon 
 the horse's back ; when the horse drew the 
 load without difficulty. I have also myself 
 observed, when going up a hill in a post- 
 chaise, that the horse with the post-poy on its 
 back drew more steadily, more firmly, and 
 with greater ease, than the other. But no 
 man, surely, would think of putting a weight 
 upon a horse's neck, in order that he might 
 have a firmer hold on the ground. Yet, in- 
 asmuch as any effect of this kind is produced 
 by horses drawing upward, it is by lifting a 
 part of the load with their neck or shoulders, 
 and, consequently, with their /or e-/<?e^ only. 
 But, as such an act would scarcely find 
 an advocate, it follows that the traces of 
 all horses drawing ought to placed in an 
 horizontal direction. 
 
 But if traces are fixed horizontally, it mat- 
 ters not, as regards the draught of the horses, 
 whether they are two yards long or six yards 
 long ; neither, if carriages travelled only on 
 roads that were perfectly flat and even, would 
 it be important whether the axles of a coach 
 
CHAP. III.] WHEEL-CARRIAGES. 33 
 
 were six feet apart, or ten feet apart, as it 
 might affect either the passengers or the 
 horses; but it is clearly demonstrable that 
 the present construction of stage-coaches is 
 extremely unfavourable to the draft of horses ; 
 that is to say, a coach standing on four 
 wheels, all as near together as they can pos- 
 sibly be set, and loaded similarly to the one 
 represented at the head of this chapter. 
 Suppose a coach, so loaded, to be travelling 
 on fair even road, each wheel bearing its just 
 proportion of the super-incumbent burthen ; 
 suddenly both the fore-wheels drop into a 
 water-gully, perhaps six inches deep ; when 
 a part, and not an inconsiderable part of the 
 load, which before rested on the hind-wheels, 
 is throw n on the fore-wheels ; whereby, when 
 most disadvantageously circumstanced, as 
 regards the horses, they are thus unfairly 
 loaded : the fore-wheels are no sooner raised 
 out of this gully, and the weight again fairly 
 divided on both axles, when, in another 
 mstant, the hind-wheels drop into the same 
 channel ; and an equal part of the load, 
 
 D 
 
34 ESSAY ON [CHAP. III. 
 
 which belonged to the fore-wheels, is thrown 
 back upon the hind-wheels. The same 
 weight, alternately bearing first on the fore- 
 wheels and then on the hind-wheels, causes 
 double labour to the horses ; that is to say, 
 the horses have, in crossing a gully, to draw 
 the same, identically the same, weight out of 
 one gully twice ; first on the fore-wheels, 
 and then on the hind-wheels. And the 
 same double operation of the load takes 
 place at every hole that may occur, on 
 either side of the coach. That this alterna- 
 tion of weight is very great, is obvious to 
 every person accustomed to ride on the tops 
 of these coaches. The outside-passengers 
 may be said to be in one constant state 
 of vacillation, not only sideways, but back- 
 ward and forward ; and at every one of 
 these backward and forward motions is the 
 effect produced as above stated ; which must 
 ever be greater, in proportion as the base of 
 the coach is small, and as the column of 
 the coach is high ; and still more, in propor- 
 tion as weight is increased at the top of the 
 column. 
 
GHAP. III.] WHEEL-CARRIAGES. 35 
 
 It may be said by Coach-Makers, and by 
 Coach-Masters, that the above remarks are 
 merely theoretical. I am however mistaken 
 if it will not be admitted, by persons conver- 
 sant with mathematics, that they amount 
 to proof that the present construction and 
 system of coaches is extremely unfavourable 
 to the horses ; and that the evil can be 
 removed only by extending the base, and 
 reducing the height of the column of the 
 coach ; or, in other words, by setting the 
 wheels further apart, and by bringing dowa 
 the load. 
 
 5. As my object is to produce a few plain 
 and intelligible remarks, it is needless to 
 enter into a discussion about the centre of 
 gravity. Every man of common sense knows 
 that a waggon, \yilh a ton of lead in its 
 bottom, and a ton of hay upon the lead, 
 would travel very safely ; whereas, if the lead 
 were on the top of the hay, it would be 
 very easily upset. Yet this is just the condi- 
 tion of one of our coaches : — light wheels 
 
 d2 
 
36 ESSAY, ETC. [chap. III. 
 
 and light frame-work ; a light body, with four 
 or at most six persons in it, and over their 
 heads at least a ton, no matter whether of 
 lead or of human beings ; twelve to sixteen 
 persons ; and not this only, for the roof is 
 frequently covered with luggage, and that, 
 again, crowded with passengers ! 
 
 I hope to be excused for once more ex- 
 claiming against this irrational, absurd, and 
 dangerous system of public conveyances ; 
 which calls loudly for the wise and judi- 
 cious interference of the Legislature. 
 
37 
 
 CHAPTER IV. 
 
 1. A new principle suggested^ as important in 
 the Construction of Carriages, viz. the Divi- 
 sion OF Weight, or Potter, hy the use of a 
 greater number of Wheels for the same load; 
 thus causing less labour to the Horses and less 
 injury to the Roads. — 2. Carriages shouldpress 
 the road with the least possible weight on any 
 one icheel. Less labour required to draw several 
 icheels in succession, over an obstruction, than 
 to draw one wheel, carrying the same amount 
 of weight, over the same object. — S, 4; 5. Il- 
 lustration of this Theory. — 6. Breadth of 
 wheels no security against the destructive 
 effects of pressure. Broad Wheels on paving- 
 stones. — 7. The principle of light pressure 
 should be carried as far as may be consistent 
 with public convenience. — 8. Light Waggons 
 for one horse suggested. — 9. Six-icheel and 
 Eight-ivheel Carriages recommended. Were 
 in use some years ago. Were remarkably 
 easy to travellers. — 10. Had one defect in 
 construction. — 11. Carried enormous loads 
 with four horses. 
 
 1. There is a principle, which I do not 
 remember to have seen noticed, and which 
 
38 ESSAY ON [chap. IV. 
 
 I consider of great importance, as applica- 
 ble to this subject. It may be called The 
 Division of Weight, or, more philosophi- 
 cally perhaps. The Division of Power : 
 that is to say, the division of the power, 
 which any carriage may possess, to crush 
 or destroy the materials of the roads ; and 
 the division of the power, which any car- 
 riage may possess, to resist the power of the 
 horses drawing such carriage. 
 
 A man can break an ordinary stick, an 
 inch in diameter, across his knee ; but, if he 
 tie ten of these sticks together, he could not 
 break them if he tried ten times, nor if he 
 tried a thousand times ; although, by these 
 thousand efforts, he might have broken a 
 thousand such sticks separately. A stone 
 might be of such a size and texture that a 
 strong man with a large hammer might 
 break it into pieces at one blow ; while a boy 
 with a small hammer, striking it with one- 
 tenth part of the force, might strike it a 
 thousand times, applying in the whole one 
 hundred times the power upon it that the 
 
CHAP. IV.] WHEEL-CARRIAGES. 39 
 
 man would have done, without producing 
 the same effect. 
 
 So it is with the pressure of wheels on the 
 materials of the roads. Suppose a stone, the 
 size of a man's fist, to lie detached on a firm 
 part of the road, and a waggon-wheel. 
 Pressing with the weight of two tons, were to 
 pass over it ; the consequence would be that 
 it would crush it to powder. But suppose 
 these two tons to be distributed into forty 
 wheelbarrows, of one hundred-weight each, 
 and they were to pass over it in succession; 
 the only effect likely to be produced would 
 be a trifling rounding of its corners : nor 
 would probably five hundred such wheelbar- 
 rows, or twenty-five tons, crush the stone so 
 completely as the single waggon-wheel. Nor 
 do I think that five hundred gig or one- 
 horse-chaise wheels, of four hundred-weight 
 each, in all one hundred tons, would so 
 completely destroy the cohesion of the stone, 
 as the single crush of the heavy wheel. 
 
 2. Conceiving, therefore, that the destruc- 
 
40 ESSAY ON [chap. IV. 
 
 tive effect of pressure on the roads increases, 
 from the lowest weights to the highest, in a 
 very rapidly increasing ratio, I think that all 
 reasonable ingenuity should be exercised, so 
 to construct our carriages as for each wheel 
 to press the road with, the least possible 
 weight that the public convenience will 
 allow. Besides, it is considered a mathema- 
 tical axiom, that action and re-action are 
 equal. If I fire a gun, the breech is pressed 
 against my shoulder with exactly the same 
 force as that with which the shot is dis- 
 charged. So, in crushing a stone with a 
 heavy waggon-wheel, just so much of the 
 power of the horses is expended and mis- 
 applied upon it as is necessary to overcome 
 the resistance occasioned by its cohesion, or 
 the firmness with which its parts were held 
 together ; whereas, if these two tons were 
 divided upon eight wheels, of five hundred- 
 weight each, the horses would draw them 
 over the stone, one after another, with 
 perhaps a tenth part of the exertion or ex- 
 penditure of strength that was necessary 
 to break the stone. 
 
CHAP. IV.] WHEEL-CARRIAGES. . 41 
 
 3. Were it necessary, I could adduce 
 practical proof of the soundness of this 
 theory. Some years ago the Brewers in 
 Bristol had, most of them, two-wheel drays, 
 carrying four barrels each, and drawn by 
 one horse, for sending out small quantities ; 
 when a friend of mine, at my suggestion, 
 had a four-wheel carriage made, the hind- 
 wheels of which were three feet high, and 
 the fore-wheels about two feet four inches 
 high; the carriage, complete, weighing about 
 eight hundred-weight ; it being about eight 
 feet long in the bed, to carry three barrels on 
 each side; which six barrels, at four hundred- 
 weight each, weighed twenty-four hundred 
 w^eight : total, thirty-two hundred-weight. 
 This w^as found easy work for one Iiorse. 
 Although firmly protested against by the 
 Man of Experience whom my friend em- 
 ployed, as a carriage that never would 
 answer his purpose, it was quickly imitated 
 by the other Brewers ; and these carriages 
 are found so completely useful and conve- 
 nient, that now (1820) they are more fre- 
 
42 ESSAY ON [chap. IV. 
 
 quently seen in the streets of Bristol than 
 any other sort. I have also proved, by 
 abundant practice, that three horses can 
 draw a ton more gross weight, on a well- 
 constructed four-wheel carriage, than they 
 can upon one with two wheels. I am not 
 aware that this is to be accounted for on 
 any other principle than that which 1 have 
 just brought forward. And as this increased 
 facility, on the part of the horses, is owing 
 to the lighter pressure of the wheels on the 
 ground ; so, in proportion as the labour of 
 the horses is lessened, is the action of the 
 wheels on the roads ; or, in other words, in 
 that proportion is the wear and tear of the 
 roads diminished. 
 
 4. Lest the principle I am desirous of esta- 
 blishing should not be clearly vmderstood, I 
 will endeavour further to explain it, with all 
 possible perspicuity. I will suppose the two- 
 wheel beer-carriage, above mentioned, to 
 weigh ten hundred-weight, and the four 
 barrels of beer to weigh sixteen hundred- 
 
CHAP. IV.] WHEEL-CARRIAGES. 43 
 
 weight : total, twenty-six hundred-weight. 
 Each wheel, then, pressed the ground with a 
 weight of thirteen hundred-weight, which 
 was the weight that the horse would have to 
 draw out of every hollow, and over every 
 obstruction, at one effort; whereas, in the 
 case of the small four-wheel carriage, the 
 horse would have to overcome the resistance 
 of only eight hundred-weight at one time ; 
 and it is proved by abundant practice, for 
 many years past, that he can draAV two of 
 these weights in succession over each ob- 
 struction, one behind the other, that is to 
 say, one on the fore- wheel and one on the 
 hind-wheel, with less labour than he can 
 draw thirteen hundred-weight over each 
 obstruction at once. 
 
 5. The Lomlon Porter-Brewers would 
 find exactly a similar result from a like 
 change. One of their two-wheel drays 
 weighs about seventeen hundred-weight ; on 
 this they load three butts of porter, at twelve 
 hundred-weight each, say thirty-six hundred- 
 
44 ESSAY ON [chap. IV. 
 
 weight: total, fifty-three hundred-weight. 
 The horses have half this load, or twenty-six 
 and a half hundred-weight, to resist, at every 
 obstruction that either of the wheels may 
 have to encounter. A four-wheel carriage 
 need not weigh more than seventeen hun- 
 dred-weighty to carry four butts : total, 
 sixty-five hundred-weiglit ; of course the 
 horses would never have to encounter more 
 than sixteen and a quarter hundred-weight 
 at any one obstruction, at one time. The 
 Brewers would find their horses draw four 
 butts much more easily, on a well-constructed 
 four-wheel carriage, than they now draw three. 
 In the construction of a four-wheel car- 
 riage for four butts, it should be remembered 
 that, whereas now each wheel has to carry 
 half the massy bed and one butt and a half, 
 — then, in the case of a four-wheel carriage, 
 as the bed would have two bearings, the 
 side-pieces or blades need not be halt^ nor a 
 quarter, so heavy as the present ; and as each 
 wheel would have to carry only its fourth 
 of a light bed, and only one butty it should. 
 
CHAP. IV.] WHEEL-CARRIAGES. 45 
 
 as well as the axles, be made proportionably 
 light. For such a carriage I would suggest 
 four feet as a suitable height for the hind- 
 wheels, and three feet for the fore- wheels. 
 And I am firmly of opinion that neither the 
 paving of the streets nor the gravel of the 
 roads would suffer a tenth so much, from four 
 wheels of sixteen and a quarter hundred- 
 weight each, whether wide or narrow, as 
 from two wheels of twenty-six hundred- 
 weight each. It is the intensity of pressure 
 that does the mischief. 
 
 6. It may indeed be argued that twenty 
 hundred-weight, on a six-inch wheel, presses 
 with the same weight, on any one point, as 
 ten hundred- weight on a three-inch wheel. 
 This would be the fact if the roads were 
 perfectly flat and smooth, and if the wheels 
 were perfectly cylindrical. It is possible to 
 make wheels perfectly cylindrical ; but it is 
 not possible to make roads perfectly flat and 
 smooth ; therefore even a cylindrical wheel 
 would rarely press alike with the whole 
 
46 ESSAY ON [chap. IV. 
 
 breadth of its rim, on the road ; but it would 
 press most heavily with one edge or the other, 
 or with some intermediate point. Hence it 
 follows that, to allow weights to increase 
 with an increased width of wheels, is to ad- 
 mit a principle which, however sound in 
 theory, is not sound in practice. But, as 
 applied to the pressure of wheels on roads, 
 as well as to the resistance they would cause 
 to the horses, the principle is not sound in 
 theory; because six-inch wheels must pass 
 over twice as mucli loose and detached mat- 
 ter as three-inch wheels ; and, whenever a 
 six-inch wheel meets a single stone, the effect 
 on that stone w ould be precisely the same as 
 though the wheel were only three inches wide. 
 In this point of view the evil of admitting this 
 principle would be two-fold, as it concerns 
 both the roads and the horses. First, the 
 evil of increased weight, which I have alluded 
 to in the first section of this chapter ; and, 
 secondly, the increased breadth of the wheel, 
 whereby twice the quantity of loose matter 
 would come within its destructive influence. 
 
CHAP. IV.] WHEEL-CARRIAGES. 47 
 
 But this theory is unsound in another point 
 of view, as apphed to roads. We are not to 
 consider roads as sohd rocks, but as quan- 
 tities of matter, very moderately cemented 
 together, and in some cases not cemented at 
 all ; therefore a great weight, in one 
 ROLLING MASS, has a tendency to disturb the 
 entire bed of the road, whether it be on a 
 six-inch wheel or on one of sixteen inches. 
 Under all these considerations, I am satisfied 
 that the only grand desideratum, on behalf 
 both of the roads and the horses, is LIGHT 
 PRESSURE. And therefore any depend- 
 ence on breadth of a\ heels, as a security 
 against the destructive effects of pressure, is 
 in my opinion fallacious. 
 
 I wish here to be understood as applying 
 tftese remarks under a supposition that wheels 
 were made upon the best philosophical con- 
 struction; that is say, perfectly cylindrical; 
 and that they stood perfectly upright or ver- 
 tical. The present system of broad wheels I 
 consider a system of mere mockery. I sup- 
 pose that not one nine-inch wheel in one 
 
48 " ESSAY ON [chap. IV. 
 
 hundred bears on the ground more than 
 three inches : that is to say, if such a wag- 
 gon were to be placed on a paving of flag- 
 stones, that the parts of each wheel in con- 
 tact with the stones would not exceed three 
 inches. It is very true that when we follow 
 such a waggon, on a Turnpike road, we 
 often see a track nine inches wide. Now 
 these wheels are round in every direction ; 
 and, generally speaking, the roads are round 
 also : it is therefore impossible for these 
 wheels to leave a nine-inch track, by any 
 other operation than that of impression, or 
 squeezing in. Whenever therefore such a 
 track is any thing more than an impression 
 in the dirt, it is an impression into the road 
 itself, by the last-mentioned operation, viz. 
 a disturbance or disarrangement of the body 
 of the road. 
 
 I have called it a system of mockery ; such 
 it really is : for there seems the most perfect 
 understanding between the mockers and the 
 mocked. I have even known Trustees of 
 Turnpike-roads make gratuitous concessions 
 
CHAP. IV.] WHEEL-CARRIAGES. 49 
 
 of half the tolls in favour of broad-wheel 
 waggons ; contrary, as it appears to me, to 
 their own special Act of ParHament. 
 
 The foregoing reasoning is also applica- 
 ble to the streets of London. It would be 
 ridiculous to insist that any advantage can 
 possibly result from the use of broad wheels 
 on these paving-stones, nearly every one of 
 which is round on its upper surface. A six- 
 inch wheel of a brewer's dray, in contact 
 with one of these stones, is merely a collision 
 of two convex bodies, each extremely hard, 
 one against another — I might almost say 
 spherical bodies ; for that is the real figure of 
 what the law supposes to be a conical wheel ; 
 and it is nearly the figure of these stones : 
 consequently the surfaces in contact, at any 
 one time, are extremely small ; little more 
 than the surfaces in contact of two eggs in 
 a basket. 
 
 7. If it be admitted as a principle of im- 
 portance, for the preservation of our public 
 roads, that the thousands of tons of commo- 
 
 E 
 
50 ESSAY ON [chap. IV. 
 
 dities of all sorts which are constantly rolling 
 over them should be divided out on as many 
 wheels as possible, it remains to be consi- 
 dered how far the principle can be carried, 
 consistently with public convenience, and by 
 what means it can be effected. 
 
 8. There are two means by which this can 
 be effected : first, by light waggons for one 
 horse ; and, secondly, by the use of carriages 
 of six or eight wheels. 
 
 One-horse-waggons fully embrace the prin- 
 ciple ; and the labour of the horses would be 
 much more efficiently applied than at present. 
 If light one-horse-waggons were constructed, 
 to weigh eight hundred-weight each, and 
 these were charged with a load of sixteen 
 hundred-weight each, a good ordinary cart- 
 horse would travel England over with such 
 a load; drawing just as much nett weight as 
 the ten horses in a heavy waggon take each 
 in gross weight ; and the roads would never 
 have a pressure, on one point, exceeding six 
 hundred-weight ! The only objection to such 
 
CHAP. IV.] WHEEL-CARRIAGES. 51 
 
 carriages that I see is, that each must be 
 attended by a man. But were they adopted, 
 roads would last — I will not say ten times 
 as long — I think they would last a hundred 
 times as long as they now do. Carriages so 
 constructed ought therefore to pass at the 
 lowest possible rate of toll. 
 
 9. The next mode is by the use of carriages 
 with six or eight wheels. About twenty years 
 ago there were several stage-coaches con- 
 structed in this manner. * Two eight-wheel 
 coaches plied some years between Bath and 
 Bristol, and they were so constinicted that 
 each wheel supported its share of the load, 
 carrying its proportion, and no more, over 
 every obstruction : the consequence was, that 
 when a wheel passed over a stone two inches 
 
 * It does not appear that these coaches were intro- 
 duced on the ground of any philosophical principle, but 
 merely as a whim of the day. Even Richard Lovell 
 Edgeworth, alluding to the existence of six-wheel and 
 eight-wheel coaches, says, "Eight wheels have been 
 applied to carriages, but it is difficult to comprehend 
 upon what principle." 
 
 s 2 
 
52 ESSAY ON [chap. IV. 
 
 high, the middle part of the carriage rising 
 only an eighth part of two inches, or one 
 quarter of an inch, they were perhaps the 
 easiest coaches, to passengers, that ever were 
 sat in. 
 
 10. They had, however, one defect in their 
 construction : which was, that the two hinder- 
 axles being fixed, whenever the coach varied 
 from a straight line on the road, the hinder- 
 most pair of wheels must have been dragged 
 sideways. How the six-wheel coaches were 
 circumstanced in this respect, I had no 
 opportunity of observing. 
 
 In constructing carriages with any number 
 of axles, the object required is for the ma- 
 chinery to be so contrived, that whenever the 
 carriage is going in a circle, if a line were 
 drawn through each of the axles, all the 
 lines should meet at one point ; which point 
 is the centre of the circle in which the car- 
 riage is travelling. In this case, every axle 
 would move fairly, without any drag side- 
 ways. 
 
CHAP. IV.] WHEEL-CARRIAGES. 53 
 
 1 1 . There is now living in Bristol a man 
 who constantly drove one of these eight- 
 wheel coaches, between that city and Bath. 
 He informs me they carried fourteen inside 
 and sixteen outside passengers, besides lug- 
 gage. With this enormous load he used to 
 go between the two cities, twelve miles of 
 road, at that time much more hilly, and in 
 worse condition than at present, with four 
 indifferent horses, in two hours. I under- 
 stand the reason why these two coaches were 
 discontinued was, that as they carried at a 
 low price, they were often filled with a crowd 
 of mean people ; which disgusted the more 
 respectable travellers, to whom alone the 
 proprietors could look for permanent custom : 
 the coaches of course dropped. This, how- 
 ever, does not affect their principle as ma- 
 chines : on the contrary, the report of them 
 tends greatly to confirm the theory I have 
 attempted to establish. 
 
55 
 
 CHAPTER V. 
 
 1, Friction does not increase with the increase 
 of the rubbing-surfaces : proved; consequently/ 
 not with an increase of the number of axles. 
 Practice of the Author. — 2. Practical use of 
 many wheels. — 3. Proposed remedy for the old 
 defect in the construction of Six-wheel and 
 Eight-wheel Carriages, illustrated by engrav- 
 ings. — 4. Causes why the Six-ioheel and Eight- 
 wheel Coaches were discontinued. — 5. Sug- 
 gestions for obviating these causes. — 6. Mat- 
 thews's Patent Coach. 
 
 1 . Here it may be proper for me to meet an 
 objection that we frequently hear advanced 
 against four-wheel carriages, viz. that, hav- 
 ing twice as many axles as a two-wheel car- 
 riage, they have proportionably more fric- 
 tion. The position stands thus : that friction 
 increases as the rubbing-surfaces increase, 
 without regard to the weight of the sliding- 
 bodies. Let a man take a common brick, 
 nine inches long, four and a half inches 
 
56 ESSAY ON [chap. V. 
 
 wide, and two and a quarter inches thick ; 
 let him draw it along a board, by means of 
 a line, over a single pulley at one end of the 
 board, and a weight falling perpendicularly 
 at the end of the cord. First, let him draw 
 it along upon its broad side : he will find 
 that it will require a certain weight to draw 
 it along the board. Then let him draw it 
 along upon its edge. He ought, upon 
 the above supposition, to find exactly half 
 the weight sufficient, because the brick is 
 now sliding upon exactly one half the sur- 
 face. Then let him draw it along upon one 
 of its ends, the brick standing upright. He 
 ought now to find one quarter of the weight 
 be first used sufficiently powerful, because 
 the brick now slides upon exactly one-fourth 
 of the extent of surface that it did in the first 
 instance ; but, instead of these results, he will 
 find that the brick will require precisely the 
 same weight to draw it along in each of these 
 experiments, provided the brick be alike on 
 all sides, not presenting any sharp points to 
 stick in the board on one side more than on 
 
CHAP, v.] WHEEL-CARRIAGES. 57 
 
 another. Therefore the friction upon any 
 number of wlieels and axles, carrying the 
 same weight in the whole, is exactly the 
 same. 
 
 I have a light waggon, about seventeen 
 hundred-weight, with turned axles, and brass 
 boxes bored to fit them; which requires 
 about an ounce of oil at a time— more 
 would be wasted. With this waggon, two 
 horses constantly fetch forty-eight bushels of 
 coals from the pit, at least two tons ; they also 
 fetch as much manure as the waggon will 
 hold, frequently more than two tons — each 
 several miles on hilly roads. 
 
 I also use olive-oil for my carts, dung- 
 carts ! Perhaps my waggon, two carts, and 
 a gig, may consume from two to three pints 
 of oil in the course of a year, at fifteen 
 pence a pint — not one shilling a piece for 
 each carriage. 
 
 I am satisfied that my two horses would 
 travel with two tons nett weight on my Avag- 
 gon, stage for stage with any road-waggon 
 in England in which the horses draw on an 
 
58 ESSAY ON [chap. V. 
 
 average not more tbc?.ri eleven or twelve 
 hundred-weight each, nett weight. Nay, 
 my Carter says he is certain that these two 
 horses could take forty-eight bushels of coals 
 (two tons,) to London, one hundred and 
 twenty miles, in four days, without any in- 
 jury or extraordinary fatigue. I mention 
 this to show how completely the horses are 
 above their work. Now, although these 
 horses might possibly draw this load in a cart, 
 it would, I think, never enter into the head of 
 a reasonable man that they could go thirty 
 miles a day with it for four days together. 
 There must, then, be an intrinsic difference 
 in favour of the waggon, whereby the horses 
 have such high command over their work, 
 which is simply this : whereas with a cart 
 of the same weight, with wheels, four feet 
 eight inches high, the horses must make an 
 exertion equal to 1609 pounds, to draw one 
 wheel over an obstruction 3 inches high ; 
 they have, in the case of the waggon the 
 fore-wheels of which are four feet high and 
 the hind-wheels five feet high, to make an 
 
CHAP, v.] WHEEL-CARRIAGES. 95 
 
 exertion equal only to 883 pounds to draw 
 one of the fore-wheels, and an exertion equal 
 only to 773 pounds to draw one of the hind- 
 wheels over such an obstruction. And if the 
 wheels were increased to six or eight, I sup- 
 pose the hoi'ses would draw the same weight 
 with nearly a proportional increase of facility. 
 And the difference, as regards the roads, 
 would be such as I have before explained. 
 
 Another thing is also obvious, viz. that if 
 these two horses drew this load in two single- 
 horse carts, each of half the weight of the 
 waggon, each horse would have exactly the 
 same exertion to make at any obstruction, as 
 though the two horses drew the whole load 
 in one cart. Hence it is evident that the 
 principle of division is equally important, 
 whether the load be great or small, or 
 whether it be drawn by a number of horses 
 or only by one. 
 
 2. But, that axle-friction, when the parts 
 are oiled, is very small, is proved by the 
 enormous weights of coals and iron-ore 
 
60 ESSAY ON [chap. V. 
 
 drawn by one horse on iron rails, or tram- 
 roads, in a series of small four-wheel car- 
 riages, one behind another, at least six in 
 number, carrying a gross weight of several 
 tons. Here, although the horse has to over- 
 come the friction of twenty-four axles, yet, 
 the major obstructions being in a great 
 degree removed, he is enabled to draw these 
 heavy weights. 
 
 .3. It would be easy to construct six-wheel 
 and eight-wheel carriages in such a manner 
 that, when turning corners, all the axles shall 
 be so many concentric radii ; or, in plain 
 words, in the case of an eight-wheel car- 
 riage, when the fore-axle shall lock three 
 
 decrees, the second axle shall lock two de- 
 cs ^ 
 
 giees, the third axle shall lock one degree, 
 and the hindmost axle shall be fixed. 
 
CHAP, v.] WHEEL-CARRIAGES. 
 
 61 
 
 E 
 
 •■-"- -Atel 
 D 
 
 -O^ 
 
 g3 
 
 SIG 
 
 -ZV 
 
 The above figure is intended to represent 
 the machinery necessary to effect the locking 
 of the wheels of an eight-wheel carriage, 
 as above described. A is the percli-bolt of 
 the fore-axle ; B the perch-bolt of the second 
 axle ; C the perch-bolt of the third axle. 
 E F is an iron brace, with a bolt and eye at 
 each end of it, to communicate motion from 
 the first axle to the second axle ; D G is a 
 similar brace, to comuumicate motion from 
 the fore-axle to the third axle. As the second 
 axle is to move two degrees when the fore- 
 axle moves three degrees, it ^vill be necessary 
 that the distance from B to F be to the dis- 
 tance from A to E as three is to two, or half 
 as much again ; and as the third axle is to 
 move one degree when the fore-axle nioves 
 
62 ESSAY ON [chap. V, 
 
 three degrees, it will be necessary that the 
 distance from G to C be to the distance from 
 A to D as three is to one, or three times as 
 much. Now, as it will be necessary, for 
 the steadiness and well-working of this 
 machinery, that the braces be set as wide 
 apart as possible, the distance from the 
 perch-bolt to the brace in the third axle 
 must be first settled, which I have taken at 
 40 inches : this will give 1 3^ inches for the 
 distance from A to D ; and as it is necessary, 
 for the even draught of the carriage, that the 
 brace-bolt E be exactly the same distance 
 from the fore perch-bolt as the brace-bolt D, 
 the distance from A to E will also be 13^ 
 inches ; and the distance from B to F, in the 
 second axle, will of course be 13 j inches 
 and half that quantity, or 20 inches. The 
 bolts must be placed exactly at equal dis- 
 tances from the centre-line of the carriage, 
 in each axle respectively, which will cause 
 the second and third axles to act with equal 
 force against each other, whereby the 
 draught on the fore-axle will be equal. 
 
CHAP, v.] WHEEL-CARRIAGES. 63 
 
 For a six-wheel carriage the same machi- 
 nery would answer very well, omitting the 
 hinder-pair of wheels. It would, however, 
 be better if it could be so managed as for 
 the third or hinder axle to be fixed, and for 
 the first and second axles only to move, as 
 thereby the carriage would turn in less 
 compass. It may be done, but not, by any 
 plan that I am aware of, without causing an 
 unequal draught on the fore-axle, because the 
 second axle must be moved by a brace on 
 one side of the perch-bolt of the fore-axle ; 
 but in this case there would be no other 
 brace to act against it. 
 
 Or, for a six-wheel carriage, the middle 
 axle might be fixed, and a contrary mo- 
 tion might be communicated from the fore- 
 axle to the hinder-axle by means of two 
 rods or braces, one passing from the near- 
 side of the fore-axle to the off-side of the 
 hinder-axle, the other passing from the 
 ofF-side of the fore-axle to the near-side 
 of the hinder-axle, crossing each other in a 
 mortise in the middle of the middle axle. 
 
64 ESSAY ON [chap. V. 
 
 Each of these rods must have a length of chain 
 at each end of it, to work on two semi-circles, 
 to be fixed on the insides of the fore and 
 hinder axles, which should not be of less dia- 
 meter than three feet. Hence the hind-wheels 
 would in all cases follow in the same track 
 as the fore-wheels, and the carriage would 
 turn in a very small compass ; but I think it 
 would be heavy and noisy, and would be 
 very liable to get out of order. 
 
 Or, for a six-wheel carriage, if the braces 
 in the above figure were brought to the dis- 
 tance of only 8 inches on each side of the 
 perch-bolt of the fore-axle ; and the perch- 
 bolt and brace in the second axle were brought 
 to a distance of 1 3y inches, w hich bears a pro- 
 portion to 8, as 5 is to 3 ; then, when the fore- 
 axle locked 5 degrees, the second axle would 
 lock 3 degrees ; and as the distance from C 
 to G in the third or hindermost axle is 40 
 inches, and the distance from A to D in the 
 fore-axle would be 8 inches, they would bear 
 a proportion to each other, as 5 is to 1: 
 consequently, when the fore-axle locked S 
 
CHAP, v.] WHEEL-CARRIAGES. 65 
 
 degrees, the third or hinder-axle would lock 
 one degree ; whereby the middle axle would 
 always form equal angles with the other two 
 axles ; that is to say, the fore-axle would 
 lock as much more than the second axle, as 
 the second axle would lock more than the 
 third axle; consequently, the three axles 
 would always form concentric radii, or nearly 
 so; and the carriage would turn in very 
 little compass, as the locking of the third or 
 hinder-axle would be very trifling. 
 
 As, in this latter application of the machi- 
 nery, the two bolts in the middle axle would 
 be each within seven inches of the center- 
 line of the carriage, attention must necessarily 
 be paid to the strength of the middle axle, 
 near these bolts. 
 
 It is scarcely needful to observe that, in 
 all these dimensions, the center of each bolt 
 is to be understood. 
 
66 
 
 ESSAY ON 
 
 [chap. V. 
 
 
 -Ol. 
 
 5 
 
 A. 
 
 B 
 
 5 
 
 D ci: 
 
 A. 
 
 S 
 
 SZL^ 
 
 TJX 
 
 "T7- 
 
 T7- 
 
 s 
 
 The above figure is intended to represent 
 the frame-work necessary for producing an 
 equal bearing of the load on each wheel of 
 an eight-wheel carriage. A A A A are four 
 pieces of wood, bearing on the first and 
 second, and on the third and fourth axles ; 
 B B are two pieces, bearing again on these. 
 These are what I beHeve the workmen call 
 the pillow-blocks, on which the bed of the 
 waggon or the springs of a coach are fixed. 
 
 5 
 
 A 
 
 T-T 
 
 A 
 
 •E± 
 
CHAP, v.] WHEEL-CARRIAGES. 67 
 
 The abve figure is intended to represent 
 the frame-work of a six-wheel carriage, 
 whereby each wheel would bear exactly 
 one-sixth part of the load. On which I need 
 only observe that the two pillow-blocks 
 marked B must be placed one third of the 
 distance, from the fore and hind-axles, res- 
 pectively, to the middle axle ; consequently 
 the fore-axle would take two-thirds of the 
 weight of the fore-end of the body, and the 
 middle axle would take one-third ; and the 
 same of the hinder-part ; therefore each axle 
 would bear one third of the whole load. 
 
 4. Should it ever, hereafter, be deemed 
 expedient to have recourse to six-wheel and 
 eight-wheel coaches, it must be kept in 
 mind that the principle I have insisted on is, 
 that an eight-wheel carriage would cause 
 less labour to the horses, and less injury to 
 the roads, than one of six wheels ; each car- 
 rying the same gross weight — that one of 
 six-wheels would cause less labour to the 
 horses, and less injury to the roads, than one 
 
 f2 
 
68 ESSAY ON [chap. V. 
 
 of four wheels ; all carrying the same gross 
 weight. 
 
 But the six-wheel and eight-wheel car- 
 riages being favourable for a long body, the 
 passengers sitting sideways, this was the 
 form, I believe, always used for these car- 
 riages some years ago ; which affords several 
 causes for their getting out of use. One I 
 have before given, in the case of the Bath 
 and Bristol coaches ; another was the circum- 
 stance of the passengers sitting sideways, 
 which was very unpleasant, particularly by 
 night ; another was, that these bodies, which 
 were ten or twelve feet long, afforded the 
 proprietors and their servants opportunities 
 of carrying enormous loads of luggage on 
 the top, beside a crowd of passengers within 
 and without, with which the poor horses 
 were expected to travel as fast as with lighter 
 coaches. Of course it is no wonder if these 
 long coaches, so unmercifully loaded, un- 
 fairly acquired the reputation of killing the 
 horses. Passengers w ere disgusted at being 
 confined, during a dark night, with a large 
 
CHAP, v.] WHEEL-CARRIAGES. 69 
 
 promiscuous company ; the side-motion at 
 the same time being very unpleasant; and 
 there being nothing to lean against, except 
 for those who could calch the ends of the 
 long seats. Under all these circumstances, 
 it is no wonder that these coaches soon 
 disappeared. 
 
 5. I see no reason why a coach-body of 
 nearly the common construction might not be 
 made wide enough to carry four passengers 
 on one seat, with a stuffed partition in the 
 middle, from the seat to the top of the coach, 
 a foot or fifteen inches wide ; which would 
 give every one a corner. A coach thus 
 formed need not exceed five feet six inches 
 in width, provided it were as wide, at the 
 backs of the seats, as across fiom door to 
 door : or, if this were inconvenient, a car- 
 riage might consist of one common six-in- 
 side body, with another body attached, for 
 passengers at an inferior price, with two 
 seats, to carry four persons each ; this body 
 to have a fixed covering or head, and cur^ 
 
70 ESSAY ON [chap. V. 
 
 tains to draw around at pleasure ; as is the 
 case with two or three pubUc coaches that 
 travel out of Bristol. This would make 
 fourteen passengers, besides one on the box, 
 with the coachman ; in all sixteen persons ; 
 enough, surely, with luggage, for four horses 
 to draw eight or nine miles an hour ! Lug- 
 gage might either be stowed below, or in 
 a chamber between the two bodies, or un- 
 der the coachman. But on the top should 
 be put neither passenger nor luggage. 
 
 It is scarcely in human nature to resist 
 temptations of gain : it is therefore necessry 
 for coach-masters to limit the accommoda- 
 tions of their carriages to such a number of 
 passengers as their horses can properly 
 draw ; otherwise their servants will take up 
 every twelve-penny passenger that offers on 
 the road ; and, let the construction of their 
 vehicles be what it may, they will find them 
 KiLL-HoRSE Coaches. 
 
 6. Perhaps, by the above suggestions, 1 
 may be thought to be proposing an in- 
 
CHAP, v.] WHEEL-CARRIAGES. 71 
 
 fringement on Matthews's Patent. I have 
 seen his coaches and have read his specifi- 
 cation, and I cannot clearly see on what 
 ground this Patent stands. It contains no 
 new principle. Stowing luggage under foot 
 is of very old date. Milton's Patent was 
 precisely this. And I have myself seen 
 travelling-carriages, many years ago, with 
 chambers for luggage under the floor of the 
 carriage. Nor is there any thing new in 
 people riding back to back, the seats being 
 placed longwise : what is called the Outside 
 Irish Car is so constructed. I have also seen 
 machines of this form for conveying military. 
 I have also seen outside-seats, back to back, 
 placed crosswise ; the double seat forming 
 one luggage-box. We have seen two close 
 bodies on the same wheels, two open bodies 
 on the same wheels, one close and one 
 open on the same wheels, others with seats 
 behind and seats before. And this coach 
 appears to me to differ from others merely 
 in the modification of the seats, but without 
 any thing, in principle, that has a claim to 
 
72 ESSAY, ETC. [chap. V. 
 
 novelty. It should also be known that to 
 every Patent is attached the following con- 
 dition, on the part of the Patentee, viz. 
 "That he is the first, and sole, inventor 
 thereof; and that the same hath never been 
 used, nor practised, by any other person or 
 persons whomsoever." Now most of the 
 particulars specified, on which Matthews's 
 Patent is founded, have been used and prac- 
 tised before: therefore I conceive that, so 
 far, his Patent is unavailing. 
 
73 
 
 CHAPTER VI. 
 
 1 . Comparative effect on the Horses, hy the use 
 of Carriages of Two zoheels, of Four wheels ^ 
 of Six wheels, and of Eight wheels, all 
 carrying the same gross weight. Illustrated 
 by a Table. — 2. Fore-wheels the pioneers of 
 the hinder-wheels. — 3. The roads doubly in- 
 terested in the question of heavy or light 
 pressure. 
 
 1. I WILL now proceed to state the practical 
 difference, to the horses, in the use of car- 
 riages of two wheels, of four wheels, of six 
 wheels, and of eight wheels ; each carrying 
 thirty hundred nett weight. I will not 
 suppose any difference in the weights of the 
 respective carriages ; because, as the num- 
 ber of wheels increases, the height, the 
 strength and weight of each wheel would be 
 proportionably reduced. Eighteen hundred- 
 weight is about the weight of a strong cart ; 
 it is also the weight of a light waggon ; nay. 
 
74 ESSAY ON [chap. VI. 
 
 heavier than one of my own, which carries 
 from two to three tons. It is also just the 
 weight of a strong stage-coach, hcensed to 
 carry six inside and twelve outside passen- 
 gers ; the average gross weight of which, 
 when loaded, may be taken at forty-eight 
 hundred-weight, although they are some- 
 times heavier. However, for the sake of 
 calculation, I will suppose a set of loaded 
 carriages, each of the weight of forty-eight 
 hundred- w eight. 
 
CHAP. VI.] WHEEL-CARRIAGES. 
 
 75 
 
 A Table, showing the power in weights descending over a 
 pulley, equal to the resistance of one wheel of a carriage 
 of several different constructions, when opposed by an 
 object three inches high, and when opposed by an object 
 an inch and a half high. The carriage in every case 
 to be forty -eight hundred-weight, gross weight. 
 
 Height 
 
 of 
 Wheels. 
 
 Weight 
 with 
 which 
 each 
 wheel 
 presses 
 the 
 road. 
 
 Weight equal 
 to the re- 
 sistance of 
 one wheel, 
 when oppo- 
 sed by an 
 object three 
 inches high. 
 
 Weight equal 
 to the re- 
 sistance of 
 one wheel, 
 when oppo- 
 sed by an 
 object 1^ in. 
 high. 
 
 /i. in. 
 
 cwt. 
 
 lb. 
 
 lb. 
 
 A Carriage with two 
 
 
 
 
 wheels 4 8 
 
 .. 24.. 
 
 ..1355 .. 
 
 .. 916 
 
 A four-wheel Coach, 
 
 
 
 
 as at present con- 
 
 
 
 
 structed : 
 
 
 
 
 The fore-wheel 8 4 
 
 .. 12.. 
 
 , . . 833 . . 
 
 , .. 552 
 
 The hind-wheel 4 8 
 
 .. 12., 
 
 . . . 677^ . . 
 
 , . . 458 
 
 Six -wheel Carriage, 
 
 
 
 
 all the wheels of 
 
 
 
 
 the same height 3 4 
 
 .. 8.. 
 
 ..555 .. 
 
 .. 368 
 
 Eight-wheel Carriage, 
 
 
 
 
 all the wheels of 
 
 
 
 
 the same height ..28 
 
 .. 6. 
 
 , . . 482 . , 
 
 , .. 313 
 
 2. Wishing to clear objections as I go, 
 it may be proper to remark, that the fore- 
 wheel is the pioneer of the hinder wheel. 
 If it meet a stone, it either breaks it down, 
 
76 ESSAY ON [chap. VI. 
 
 in some degree, or pushes it aside ; or, if 
 it be lieavy dirt, it clears the way ; whereby 
 the hind-wheels have, rarely, much resist- 
 ance of this kind, if the wheels follow 
 well. It is fifty to one if the hind-wheel 
 meets the same obstruction, under precisely 
 the same circumstances, as the fore-wheel 
 did, excepting only on hard pavements. 
 And even these reduced obstructions are 
 to be encountered at renewed efforts, as 
 before explained. The coachmakers ac- 
 cordingly find the fore-wheels of coaches 
 wear out much faster than the hinder ones. 
 Taking the above table to be correct, 
 I think there can be but one conclusion 
 drawn from it, viz. that carriages bearing 
 the same weight may be drawn with greater 
 ease, in proportion as the number of wheels 
 is increased. In the case of the coach, 
 for instance : the fore-wheel of a common 
 stage-coach requires a power to draw it over 
 an obstruction, whether high or low, com- 
 pared with the power necessary to draw 
 the fore-wheel of an eight-wheel coach of 
 
CHAP. VI.] WHEEL-CARRIAGES. 77 
 
 only two feet eight inches high, each coach 
 carrying the same weight, as seven is to 
 four. 
 
 As the very principle on which my reason- 
 ing proceeds is to " Divide and Conquer," 
 that is to say, as any given power will 
 overcome a much greater weight, when that 
 weight is divided, than when it is entire, — it 
 is almost superfluous to admit that the sum 
 of the powers required to draw four wheels of 
 an eight-wheel coach, over an obstruction 
 in succession, is greater than the sum of the 
 powers required to draw the fore and hind- 
 wheels of a coach, as at present constructed, 
 each coach weighing forty-eight hundred- 
 weight : the former requiring, for a 3-incli 
 obstniction, 1 928 pounds ; and the latter 
 requiring only 1310 pounds. I will take a 
 fourth of these weights, to reduce them 
 within the power of a man : that will give, 
 on account of the four wheels of an 
 eight-wheel coach, four several weights 
 of 120 pounds each ; and, on account of 
 the two wheels of a four-wheel coach, the 
 
7s ESSAY ON [chap. VI. 
 
 two several weights of 208 pounds and ] 69 
 pounds. Now, by how much a man could lift 
 120 pounds, four times in succession, more 
 easily than he could lift the two several 
 weights of 208 pounds and 169 pounds, once 
 each, in succession, — ^by so much could the 
 horses draw the eight-wheel coach more 
 easily than they could draw the four-wheel 
 coach, over such obstruction. 
 
 The force of this reasoning must I think, be 
 obvious to every person conversant with such 
 matters : it applies to labour of every kind. 
 A man can dig a much greater quantity of 
 ground in a day, with a spade considerably 
 below his strength, than he can with one 
 equal to his strength. Two men at a crane 
 can lift a much greater quantity of goods 
 to a given height, in the course of a day, 
 in such portions, as they can lift with ease 
 at each time, than they can if the crane be 
 so loaded as to oblige them to exert their 
 strength to the utmost. And I think it must 
 be equally obvious that four horses, drawing 
 an eight-wheel coach with wheels two feet 
 
CHAP. VI.] WHEEL-CARRIAGES. 79 
 
 eight inches high, can apply a power equal 
 to 482 pounds four times, in drawing such 
 coach over an obstruction three inches high, 
 with much less labour than that which they 
 must exert in two efforts equal to the several 
 weights of 833 pounds and 677^ pounds, in 
 drawing the two wheels of a four-wheel 
 coach, as at present constructed, over a 
 similar object ; notwithstanding the amount 
 of the power in the four efforts in the former 
 case, exceeds that of the two efforts in the 
 latter case. 
 
 3. As the foregoing calculations concern 
 the roads, the consideration is, in my opinion, 
 of high national importance : for it must be 
 kept in mind that the respective powers, as 
 set down in this last table, as necessary to 
 draw any wheel over an obstruction, are 
 actually exerted. The road itself is the 
 fulcrum ; and the horses' limbs are the levers. 
 The road itself is acted against by the horses' 
 shoes, in proportion to the pressure and 
 .grinding property of the wheel ; and this 
 
80 ESSAY, ETC. CHAP. VI. 
 
 takes place all the way down, from the 
 heavy waggon, with its drug-mill-wheels, to 
 the light gig. It is road against road ; 
 action and re-action being, in every case, 
 exactly equal. Therefore the road must 
 ever be considered as doubly interested in 
 this important question. 
 
81 
 
 CHAPTER VII. 
 
 1. Tolls should he imposed on Wheels only, 
 loithout regard to the number of horses draw- 
 ing any carriage. — 2. A liberal number of 
 horses, to any carriage, advantageous to the 
 Road. — 3. Eight-Wheel Carriages, to weigh 
 forty -eight hundred weight gross, ought to be 
 encouraged by low tolls, as most advantageous 
 to the Proprietors, and to the Roads. — 4. If 
 intensity of pressure on each wheel be re- 
 moved, the form or width of the wheel is of 
 little consequence. — 5. Cylindrical wheels pre- 
 ferable, even for the lighest weights. 
 
 ]. It is a maxim with me, that sound prac- 
 tice must ever accord with sound theory. 
 Now if it be admitted that the theory I have 
 attempted to establish be correct, and that, 
 as far as practice can be brought in confir- 
 mation of it, I have shown that the division 
 of weight on a number of wheels is practi- 
 cally best, both for the horses and for the 
 roads ; it follows that the principles on 
 
 G 
 
82 ESSAY ON [chap. VII. 
 
 which our Turnpike- Acts are founded, as 
 far as they tend to encourage the use of 
 carriages of one description, and to discou- 
 rage those of another, are entirely erroneous. 
 I conceive that the tolls should be imposed 
 on the wheels only, without regard to the 
 number of horses; because upon the principle 
 before mentioned, that action and re-action 
 are equal, the quantity of power actually 
 used or expended, to draw any particular 
 carriage, can only be equal to the resistance 
 of that carriage. 
 
 2. If an extra number of horses be ap- 
 plied to a broad-wheel waggon, the owner 
 is liable to be fined. Suppose eight horses 
 to be the limited number : in going up-hill 
 they are perhaps obliged to exert themselves 
 to the utmost, to draw the load after them ; 
 but if sixteen horses were used in ascending 
 this hill, still no more power would be ap- 
 plied to the waggon ; each horse would then 
 exert himself only half as much as in the 
 case of the eight horses ; and consequently 
 
CHAP. VII.] WHEEL-CARRIAGES. 83 
 
 the strain of the horses' feet against the 
 ground, at any one point, would be only 
 half so much. But, upon the principle I 
 have before urged respecting the division of 
 power, the injury done to the road from this 
 cause, would not perhaps be one twentieth 
 part so much, as in the case of only eight 
 horses. 
 
 3. I consider that an eight-wheel coach, 
 carrying gross weight forty-eight hundred- 
 weight, would run easier to the horses, in a 
 very great degree, than a four-wheel coach 
 of the same weight. I consider also that an 
 eight-wheel waggon, to weigh itself sixteen 
 hundred-weight, carrying thirty-two hun- 
 dred-weight of goods, might be easily drawn 
 by two ordinary cart-horses, at the usual 
 rate of road waggons ; four-wheel waggons, 
 carrying several hundred-weights more than 
 half that weight, being now drawn by one 
 horse — that such a carriage might be driven 
 by a man on the box ; and that it would 
 answer all the purposes of the public carriers, 
 G 2 
 
84 ESSAY ON [chap. VII. 
 
 it being several hundred-weight per horse 
 more than they usually draw — that carriages 
 of this description, with springs, might also 
 be used, by the public carriers, with four light 
 horses, at the rate of six miles an hour — 
 that, by the introduction of such carriages, 
 the traveller would be relieved from one of 
 the greatest annoyances he has to encounter, 
 viz. the gothic, broad-wheel waggon. That 
 therefore carriages, bearing on the road at 
 the rate of six hundred-weight per wheel 
 should pass at the lowest rate of toll ; and 
 that on all wheels above that weight the 
 tolls should be increased. 
 
 4. We need not, then, trouble ourselves 
 about the shape or breadth of wheels. If 
 we get rid of heavy pressure, we gain a 
 great point. Even a drug-mill cannot grind, 
 unless it be heavy. And it happens that, the 
 narrower the wheel, the less is the twist ; 
 consequently, wheels that are both light 
 and narrow cannot do much mischief. 
 
CHAP. VII.] WHEEL-CARRIAGES. 85 
 
 5. Nevertheless, I mean not to plead for 
 dishing wheels, however small they may be, 
 or however lightly they may press on the 
 roads ; it being shown before, that upright, 
 cylindrical wheels, whether wide or narrow, 
 with axles perfectly straight, and with cylin- 
 drical ends, being the only form that has a 
 natural tendency to roll straight forwards, 
 should always be used ; as they must, under 
 every circumstance , be less injurious to the 
 roads, and, in that degree, must cause less 
 labour to the horses than wheels of any 
 other form. 
 
87 
 
 CHAPTER VIII. 
 
 1. Principle on which Tolls ought to he imposed. 
 — 2. How a Table of Tolls ought to be calcu- 
 lated, to meet this principle. — 3. A Table of 
 Tolls, calculated on this principle. — 4. Ope- 
 ration of Tolls so calculated. Opinion of 
 John Louden M'^Adam. — 5. Opinion of the 
 Legislature, in I8th Geo. III. on the injury 
 caused by excessive zceights. Sixteen-inch 
 rollers, as now constructed, liable to an addi- 
 tional toll of Forty Pounds. — 6, Breadth 
 of Wheels no security against the destructive 
 effectof pressure, further shown, — 7. Probable 
 reasons why Heavy Waggons were formerly 
 encouraged. — 8. Wheels of light pressure 
 more urgently necessary, where the materials 
 for roads are of a soft and bad quality. 
 
 1. In suggesting the adoption of a new 
 principle on which to levy tolls on carriages, 
 it is proper that I should explain the reasons 
 for which I venture to suggest it. 
 
 A Turnpike-road is proposed to be made ; 
 and, in order to purchase the necessary lands 
 and to procure labour and materials to 
 carry the work into effect^ funds must be 
 obtained ; for which purpose, money is bor- 
 
88 ESSAY ON [chap. VIII. 
 
 rowed ; and the lolls to be collected are 
 pledged to the lenders, to pay not only the 
 interest, but, by degrees, the principal also. 
 The tolls therefore ought to be levied on 
 every carriage, at such a rate as will repair 
 the damage done by such carriage in tra- 
 velling over it ; and a further additional sum 
 towards the interest and principal of the bor- 
 rowed money, and no more. It ought not 
 therefore, in my opinion, to be taken into 
 account, with what the carriage is loaded, 
 that is to say, whether it be loaded with 
 human beings, or with manure, or with any 
 kind of merchandize — whether it be a cart 
 or a gig, a coach or a waggon. The only 
 consideration ought to be, how much money 
 will it require to repair the damage done 
 by such vehicle to the road, together with 
 a reasonable sum for the other purposes. 
 This, as I have before stated, is to be esti- 
 mated only by the number of the wheels, 
 and the weight with which they respectively 
 press the road ; without any regard what- 
 ever to the number of horses drawing such 
 carriage. 
 
CHAP. VIII.] WHEEL-CARRIAGES. 89 
 
 It is time that the principle, and also the 
 practice, of favouring one species of com- 
 merce at the expense of another, were en- 
 tirely laid aside. But, to be consistent, if vre 
 suiFer manure to pass toll-free, in order that 
 the necessaries of life may be rendered at a 
 low price, we ought also to grant the same 
 indulgence to live cattle ; to butchers' carts ; 
 to millers' carts and waggons ; to farmers' 
 carts and waggons, carrying corn, potatoes, 
 turnips, carrots, and cabbages ; to the thou- 
 sands of market-carts, with butter, eggs, 
 veal, pork, poultry, &c. ; to bakers' carts ; to 
 brewers' drays ; to carts and waggons loaded 
 with coals and other fuel; to carriages 
 loaded with wool or flax, raw and manu- 
 factured. And, as houses to live in are also 
 necessaries of life, we ought to exempt 
 building-materials of all descriptions, viz. 
 stones, bricks, tiles, lime, sand, and timber. 
 
 2. In making out a Table of Tolls, it 
 ought, upon the principle I have laid down, 
 so to be calculated as to encourage, as much 
 
90 ESSAY ON [chap. VIII. 
 
 as possible, the greatest division of weight ; 
 so that it should never be the interest of the 
 owner of any carriage to lessen his number 
 of wheels: that is to say, that any given 
 weight shovild always pay less toll on eight 
 wheels than on six wheels, and less toll on 
 six wheels than on four wheels, and less 
 toll on four wheels than on two wheels, 
 
 3. A Table of Tolls, calculated in the 
 following proportions, would effect this 
 object, viz. 
 
 Weight Increased 
 
 in Cwts. Toll. Total Toll. 
 
 For every pair of wheels 
 bearing on the ground 
 
 with a weight not £ s. d. £ s. d. 
 
 exceeding 12 . . . . 2 
 
 Ditto 14 . . Of . . 2i 
 
 Ditto 16 . . 1 . . 3i 
 
 Ditto 18 . . li . . 5 
 
 Ditto 20. .0 2 ..o 7 
 
 Ditto 22 . . 3 . . 10 
 
 Ditto 24. .0 4 ..0 1 2 
 
 Ditto 26. .0 5 ..0 I 7 
 
 Ditto 28. .0 6 ..0 2 1 
 
 Ditto 30 ..0 7 ..0 2 8 
 
 Ditto 32 ,.0 8 ..0 3 4 
 
 Ditto 34 ..0 9 ..0 4 1 
 
CHAP. VIII.] WHEEL-CARRIAGES. 
 
 91 
 
 
 Weight 
 in Cwts. 
 
 Increased 
 Tolls. 
 
 Total Toll. 
 
 For every pair of wheels 
 
 
 
 
 
 
 
 bearing on the ground 
 
 
 
 
 
 
 
 with a weight 
 
 not 
 
 
 =£ 
 
 s. 
 
 d. 
 
 £ 
 
 i. d. 
 
 exceeding .... 
 
 
 36 . 
 
 . 
 
 
 
 10 . 
 
 
 
 4 11 
 
 Ditto 
 
 
 38 . 
 40 . 
 
 
 . 
 
 
 
 11 . 
 . 
 
 
 
 
 5 10 
 
 Ditto 
 
 
 6 10 
 
 Ditto 
 
 
 42 . 
 
 
 
 
 1 
 
 
 
 7 11 
 
 Ditto 
 
 
 44 . 
 
 
 
 
 2 
 
 
 
 9 1 
 
 Ditto 
 
 
 46 . 
 
 
 
 
 3 . 
 
 
 
 10 4 
 
 Ditto 
 
 
 48 . 
 50 . 
 
 
 . 
 
 
 4 . 
 
 5 . 
 
 
 
 
 11 8 
 
 Ditto 
 
 
 13 1 
 
 Ditto 
 
 
 52 . 
 
 . 
 
 
 6 . 
 
 
 
 14 7 
 
 Ditto 
 
 
 54 . 
 
 . 
 
 
 7 . 
 
 
 
 16 2 
 
 Ditto 
 
 
 56 . 
 
 . 
 
 
 8 . 
 
 
 
 17 10 
 
 Ditto 
 
 
 58 . 
 
 
 
 
 9 . 
 
 
 
 19 7 
 
 Ditto 
 
 
 60 . 
 
 . 
 
 
 10 . 
 
 
 1 5 
 
 Ditto 
 
 
 62 . 
 
 . 
 
 
 11 . 
 
 
 3 4 
 
 Ditto 
 
 
 64 . 
 
 
 
 2 
 
 . 
 
 
 5 4 
 
 Ditto 
 
 
 66 . 
 
 . 
 
 2 
 
 1 . 
 
 
 7 5 
 
 Ditto 
 
 
 68 . 
 70 . 
 
 . 
 . 
 
 2 
 2 
 
 2 . 
 
 3 . 
 
 
 9 7 
 
 Ditto 
 
 
 11 10 
 
 Ditto 
 
 
 72 . 
 
 . 
 
 2 
 
 4 . 
 
 
 14 2 
 
 Ditto 
 
 
 74 . 
 
 . 
 
 2 
 
 5 . 
 
 
 16 7 
 
 Ditto 
 
 
 76 . 
 
 . 
 
 2 
 
 6 . 
 
 
 19 1 
 
 Ditto 
 
 
 78 . 
 
 . 
 
 2 
 
 7 . 
 
 2 
 
 1 8 
 
 Ditto 
 
 
 80 . 
 
 . 
 
 2 
 
 8 . 
 
 2 
 
 4 4 
 
 Excepting, only, when a load consists of one 
 undivided mass ; as a block of stone, one 
 
92 ESSAY ON [chap. VIII. 
 
 single piece of iron-work, one piece of tim- 
 ber, or the like ; in which case it should be 
 allowed to pass at a certain moderate toll, 
 say at thirty hundred-weight per pair of 
 wheels. 
 
 4. The Reader will see that, by the above 
 Table, eight-wheel carriages might pass 
 with very heavy loads, at a very moderate 
 toll : even four tons might pass for 2s. 4d. ; 
 while a four-wheel waggon, weighing eight 
 tons, would pay £4 Ss. Sd. My friend, 
 John Loudon M^'Adam,* the General Sur- 
 veyor of the Bristol Turnpike-roads, gives 
 me as his opinion. That the only waggon 
 of this description, which travels between 
 London and Bristol, does more injury to the 
 roads than all the other cartilages on the 
 road put together, distance for distance. 
 If this opinion be correct, and I have no 
 
 * This gentleman is the well-known promoter of the 
 new system of constructing roads, which may be consi- 
 dered as the commencement of a new sera in this 
 important branch of science. 
 
CHAP. VIII.] WHEEL-CARRIAGES. 93 
 
 doubt but it is, such toll would be but 
 fairly and moderately imposed. 
 
 5. It is plain that in the 13th year of Geo. 
 III. the Legislature were aware of the great 
 injury sustained from excessive weights, by 
 their imposing an additional toll of twenty 
 shillings 'per hundred-weight on all over- 
 weights ; but they were not aware that the 
 injury regularly increased, in an increasing 
 ratio, from the lowest weights to the high- 
 est ; or it does not seem that they knew how 
 to meet the evil. It is on this last-mentioned 
 principle that the above ^Table of Tolls 
 proceeds. 
 
 Besides, as sixteen-inch rollers, contrary 
 to the express letter of the Statute, do not 
 bear with their whole breadth on the road ; 
 we have a right to consider eight tons, as 
 carried on nine-inch wheels ; we shall then 
 find the overweight to amount to two tons, 
 which, at twenty shillings per hundred- 
 weight, would be forty pounds! which is 
 the toll really intended by the Legislature 
 
94 ESSAY ON [chap. VIII. 
 
 to be imposed ; and which, according to the 
 true intent and meaning", as well as the 
 letter, of the Statute, they are liable to pay. 
 
 6. I have said (Chap. IV. § 6) « The 
 present system of broad wheels I consider a 
 system of mere mockery ;" of which opinion 
 the above-stated fact is an abundant confir- 
 mation. In short, if the Law were literally 
 obeyed, if wheels were made ^perfectly coni- 
 cal, bearing with their whole breadth on the 
 surface of the road, the injury caused to the 
 roads would be ten times greater than it 
 now is from the action of those wheels ; 
 because the dragging backward and for- 
 ward, or twist, would be incomparably 
 f^reater at tlie sides of each wheel than at the 
 middle of the rim : whereas, by the present 
 construction, the edges of the rim do not 
 touch the road. (See Chap. IL § 1 , et seq.^ 
 The injury to the roads would also be in- 
 creased tenfold, from the increased labour 
 of the horses in drawing carriages with 
 wheels so constructed. The fact is, that no 
 
CHAP. VIII.] WHEEL-CARRIAGES. 95 
 
 NO WHEEL, generally speaking, whether it be 
 six inches wide, or nine inches wide, or six- 
 teen inches wide, does bear on a flat and 
 even surface more than about three inches. 
 Therefore, whether the Law, as it now 
 stands, be strictly enforced, or whether, as 
 at present, it be universally evaded, it must 
 be evident that breadth of rim, in either 
 case, can be no security against the destruc- 
 tive effects of pressure. 
 
 7. When we consider the state of the 
 roads throughout England forty or fifty years 
 ago, it is not wonderful that the Legislature 
 should have encouraged the use of heavy 
 broad-wheel waggons by low tolls, and even 
 by a total exemption from tolls ; the motive 
 for which evidently was, to break down the 
 large stones which at that time were thrown 
 upon them, as well as to press in the sides of 
 the deep ruts which every where abounded ; 
 and that these were the objects, especially 
 the latter, is further evident, by their per- 
 mitting waggons with nine-inch-wheels, so 
 
96 ESSAY, ETC. [chap. VIII. 
 
 adjusted as to roll a surface of sixteen inches 
 on each side, to pass at reduced tolls. But 
 it is difficult to assign any reason why they 
 fixed the maximum-weight of these favoured 
 vehicles at eight tons, imposing on them 
 the enormous fine of twenty shillings per 
 hundred- weight, from eight tons upward. 
 
 8. I am aware that it will be objected, by 
 persons resident in districts where the mate- 
 rials for roads are of a soft and bad quality, 
 and where the roads are consequently deep 
 and rutty, that the light wheels I propose 
 would be buried in the ruts ; and that such 
 wheels could therefore never be used. To 
 such I would state what I conceive to be a 
 parallel case. Suppose a Farmer to have a 
 very tender meadow, and he were to turn in 
 heavy oxen ; the consequence would be that 
 these oxen would break the turf at every 
 step, and tread it perhaps six or eight inches 
 deep ; whereas if this meadow were grazed 
 with sheep, the surface of the meadow 
 would be uninjured. Now it should be 
 
CHAP. VIII.] WHEEL-CARRIAGES. 97 
 
 remembered that the hoof of the ox as much 
 exceeds that of the sheep, as the weight of 
 the former does that of the latter ; but, as in 
 the case of the heavy wheel, it is the inten- 
 sity of pressure in one mass which does the 
 mischief; which is by no means compensated 
 by the breadth of the wheel in one case, 
 nor by the size of the lioof in the other. 
 Nor, if the weight of all the sheep in 
 the meadow were equal to that of all 
 the oxen, would the damage done by the 
 former bear any proportion to that done by 
 the latter : just as I have before stated, 
 the damage done to roads by light wheels 
 would bear no proportion to that done by 
 heavy ones, although in both cases the sum 
 of the weights passing over a road might be 
 equal. Therefore, wherever the materials 
 are bad, and the roads liable to become 
 foundrous, it is exactly in that proportion 
 more and more important that wheels of 
 light pressure should be used. As in the 
 ease of the meadow, the softer it is, the 
 
 H 
 
98 ESSAY, ETC. [chap. VIII. 
 
 lighter should be the tread of the animals 
 with which it is depastured. The fact is 
 that, if wheels of light pressure only were 
 used on such roads, it is not likely that 
 deep ruts would ever be formed. 
 
99 
 
 CHAPTER IX. 
 
 1. SpringSj their use explained. How they 
 operate to the ease of the Rider. — 2. Richard 
 LovELL Edgeworth's Experiment on Springs. 
 
 1. It is agTeed by philosophers that there 
 is in all matter a tendency to continue in 
 the state in which it is, whether of motion or 
 of rest. It requires more power to move a 
 coach or otiier body from a state of rest than 
 is afterwards required to keep it in motion. 
 Thus we see that horses always exert much 
 more power to start a carriage, whether a 
 waggon or a coach, than is afterwards re- 
 quired to continue it in motion ; and, when 
 in motion, a considerable effort is frequently 
 necessary to stop it. 
 
 When a coach is going with very great 
 speed along a straight road, and suddenly 
 turns a corner, such is its tendency to con- 
 tinue its former course, that coaches have 
 often been overturned from this cause alone. 
 
 H 2 
 
100 ESSAY ON [chap. IX. 
 
 This principle applies to every variety of 
 motion to which a carriage is hable in 
 travelHng. But if a carriage be furnished 
 with springs, although they may be bent, 
 equal to the pressure of the simple weight of 
 the load, it is found, by experience, that 
 the load, rather than alter its course, by 
 suddenly rising over a stone, will bend the 
 springs still farther ; whereby, in passing 
 over a stone four inches high, the load may 
 not perhaps rise more than one inch : the 
 springs in this case giving way an extra 
 three inches. And I think I have known 
 the springs of a stage-coach, loaded with 
 about a ton, when passing quickly through 
 a gully or water-course, across a turnpike- 
 road, by first descending suddenly into the 
 gully, and then as suddenly rising out of 
 it, to bend equal to a dead pressure of three 
 tons. And in proportion as it is more easy 
 for the springs to bend than for the weight 
 to vary from its course, in that proportion 
 is the labour of the horses lessened by the 
 use of them. 
 To the above-mentioned principle it is 
 
CHAP. IX.] WHEEL-CARRIAGES. 101 
 
 that we are indebted for the ease with which 
 we ride on springs. By how much the 
 springs give way to all the little stones and 
 other inequalities of the road, by so much 
 do we pass on in an even or horizontal line, 
 more than we otherwise should. For if our 
 roads were perfect mathematical planes, and 
 if wheels were perfect mathematical circles, 
 springs would be useless appendages to any 
 carriage, as they could in no degree add to 
 the ease of the traveller, nor could they 
 lessen the labour of the horses. 
 
 2. Richard Lovell Edgeworth details some 
 curious experiments on the subject of springs; 
 the result of which is, that the advantage 
 from the use of springs, when a carriage is 
 going on a rongh road, at the rate of 3^ 
 miles per hour, is, compared with a carriage 
 without springs, as 12 is to 8. When going 
 at the rate of 5^ miles per hour, the advan- 
 tage is double, or as 12 is to 6. 
 
 From which results, some very important 
 considerations arise. If, as I have above 
 
102 ESSAV, ETC. [chap. IX. 
 
 stated, springs could be of no use, provided 
 the roads were perfect mathematical planes, 
 and provided wheels were as perfect circles ; 
 and if it be also true, as I have stated 
 (Chap. I. § 8) that although a wheel may 
 be carried over a stone by the momentum 
 of the carriage ; yet that the momentum 
 thereby lost must be restored by extra exer- 
 tions of the horses; and that this is true is 
 evident, otherwise a carriage, travelling with 
 great speed, would require no more power to 
 draw it on a rough road than on a smooth 
 one ; and if it be also true that a carriage 
 without springs, going on a rough road at the 
 rate of 5|^ miles per hour, requires double 
 the labour that it would require if constructed 
 with springs ; and as a very great proportion 
 of all carriages have no springs, — how impor- 
 tant is it that our roads should be brought 
 as nearly as possible to the state of mathema- 
 tical planes ! and in order that they may be 
 preserved in this order, that all carriages 
 should be so constructed as to cause the least 
 possible wear and tear upon them. 
 
103 
 
 CHAPTER X. 
 
 1. Suggestions respecting the Tax on Stage- 
 Coaches. — 3. Private Carriages. Taxed 
 Carts. 
 
 1. I HAVE already hinted that I think it 
 unreasonable and barbarous, that persons 
 who cannot afford to pay the highest price 
 for conveyance by stage-coaches should, 
 because they are poor, be necessarily exposed 
 to the severity of the weather; and that 
 therefore every public carriage ought to be 
 so constructed as to afford shelter for every 
 passenger ; but, as the Law now stands, the 
 Proprietors of Stage-Coaches are compelled, 
 if they carry more than the inside of the 
 coach v\^ill hold, to carry the rest on the 
 outside, I therefore think that the license, 
 instead of being granted to carry, say six 
 inside and twelve outside, should be general : 
 that is to say, to carry eighteen passengers; 
 for which the Coach-Master should pay the 
 same tax as he now does. 
 
104 ' ESSAY ON [chap. X. 
 
 2. Then, as regards private carriages, 
 coaches, chariots, and one-horse chaises, I 
 take the Hberty respectfully to suggest, to 
 those in authority, that the tax ought not to be 
 so imposed as to Hmit the number of wheels ; 
 for two reasons : the first is to be found in 
 the principle I have endeavoured to establish, 
 viz. that the greater the number of w^heels, 
 on which any given weight is laid, the better 
 for the road. Now, although this considera- 
 tion may be trifling, as regards carriages 
 calculated to carry only two or three persons 
 each ; yet it is a consideration, and it ought ^ 
 ever to be kept in view. The second reason 
 is the consideration of danger attendant on 
 two-wheel carriages ; which is so great, and 
 so obvious, and which is so frequently con- 
 firmed by the most frightful accidents, that 
 it is needless to enlarge upon it. I therefore 
 think that as the tax on all these vehicles is 
 imposed, as on articles of luxury, the tax 
 ought to be laid on in proportion to the 
 luxury ; which is certainly to be estimated 
 by the number of horses drawing, and not 
 
CHAF. A.J WHEEL-CARRIAGES. 105 
 
 by the number of wheels on which a car- 
 riage stands : in the following manner ; say, 
 
 £ t. d. 
 For every Carriage having steel-springs and 
 
 drawn by only one horse 
 
 Drawn by two or more horses 
 
 For every Carriage constructed without lin- 
 ing or ornament, or steel springs, (but 
 without limitation of number of wheels, 
 or of cost) 
 
 I do think that, on the ground of huma- 
 nity, in the case of this last-mentioned vehicle, 
 neither wooden springs, nor cushions, nor 
 head, nor apron, ought to be proscribed. It is 
 not likely that many persons, who can afford a 
 better, would submit to so humble a carriage 
 as must necessarily be made under these 
 limitations. And it should be remembered 
 that many females, in slender circumstances, 
 are quite as tender as some who are blessed 
 with affluence, and who consequently can af- 
 ford an easy and luxurious coach. Having 
 myself occasionally been exposed to the ne- 
 cessity of riding in a taxed cart without any 
 
106 ESSAY, ETC. [chap. X. 
 
 springs, I can say the sensation was dread- 
 ful. I therefore think that the use, either 
 of wooden springs, or of cushions, or of 
 shelter from the weather, ought neither to 
 be forbidden to any fellow-creature, nor, 
 which is the same thing, to be put out 
 of his reach by the operation of a severe 
 tax. 
 
J or 
 
 CHAPTER XI. 
 
 1. Mechanical Action of Wheels on the Mate- 
 rials of Roads explained. — 2, Narrow Roads, 
 why so frequently in bad condition. Deep 
 ditches and sudden falls of the ground, close 
 to the sides of roads, productive of ruts. — 
 3. Convex Roads never wear well, and why. 
 — 4. Materials for Roads. Laying on of 
 Materials. — 5. Whether a thick or thin cover- 
 ing at one time. — 6. Whether the whole 
 breadth of a road, or only half of it, should 
 be covered at one time. 
 
 Although it was my intention, when I took 
 up my pen, to confine myself solely to the 
 subject of Wheel-Carriages ; yet, having 
 had great opportunities of making observa- 
 tions on Roads, I am induced to add a few 
 remarks thereon. 
 
 1. It would have been proper, when 
 treating on the form and constmction of 
 wheels, to have explained the mechanical 
 operation of wheels on the materials of roads. 
 
108 ESSAY ON [chap. XI. 
 
 The action of wheels on the materials of 
 roads is twofold, viz. Finessing and Grind- 
 ing. The Jirst is when a wheel passes over 
 any material without any twist, or drag, or 
 slide, as would be the case with Avheels 
 made perfectly cylindrical, and standing 
 upright. Grinding may, I believe, in every 
 case be defined to be the effect produced on 
 any substance interposed between two bodies, 
 one of which has a sliding motion, yet so 
 firmly confined or pressed betAveen them, that 
 the moving body cannot slide over the inter- 
 posed substance ; but, in consequence of the 
 pressure, the interposed substance, adhering 
 firmly both to the fixed and to the moving 
 body, is necessarily lacerated or torn asunder, 
 and reduced to atoms. This is the process 
 in Corn-Mills, in Drug-Mills, in Barilla- 
 Mills, and in every other Mill, properly so 
 called.* 
 
 * Steel Mills, for grinding pepper, coffee, &c. have 
 very little of this lacerating principle in them. They 
 divide substances by the action of sharp edges one against 
 another, like so many pairs of scissars : they are rather 
 cutting-machines than mills. 
 
CHAP. XI.] WHEEL-CARRIAGES, 109 
 
 But, although the ingenious Author I have 
 before cited has very aptly compared broad 
 conical wheels to drug-mills, he was not 
 aware how the destructive effects of them 
 are produced.* I remember frequently, when 
 a boy, to have trodden with one heel on 
 a piece of soft brick, or *of dry old mortar, 
 which was firm enough to bear the weight 
 of my body, uninjured ; but, on giving my 
 body a swing round with my other foot, I 
 have instantly reduced it to powder. The 
 action in this case is very obvious: the 
 weight of my body confined the piece of 
 brick firmly to the ground ; my heel was also 
 pressed by the same weight firmly upon the 
 brick : one part of the brick therefore re- 
 maining confined to the ground, and the 
 other part being carried round by my heel, 
 the brick of course was torn asunder and 
 reduced to powder. But, were I to try the 
 
 ***Wedo not know with much precision why the 
 twisting or spiral motion here alluded to tends to overcome 
 the attraction of cohesion ; but we know with certainty 
 that the fact is so/' — Edgeworth 07i Wheel-Carriages. 
 
110 ESSAY ON [chap. XI. 
 
 same experiment with a piece of limestone, 
 I should find that the friction of my foot 
 would not overcome the attraction of cohe- 
 sion in this material ; but my body might 
 swing round, my heel shding upon the stone 
 without injuring it. A similar operation 
 would however produce a like destructive 
 effect on the limestone, provided the moving 
 body were pressed with such a weight that, 
 rather than slide upon it, the attraction of 
 cohesion in the stone would give way. In 
 other words, the harder the substance is, the 
 heavier and more powerful must the mill 
 be to grind it ; and, consequently, the 
 heavier and more powerful is the mill, and 
 the heavier and more powerful is the cart- 
 wheel, the more efficacious in the work of 
 destruction will they necessarily be. This I 
 conceive is a simple elucidation of the differ- 
 ence between Pi^essing and Grinding, and 
 this is the difference of the effects on the 
 materials of our roads, produced by the use 
 of upright cylindrical wheels, which act only 
 by Pressure, and by the use of conical 
 
CHAP. XI.] WHEEL-CARRIAGES. HI 
 
 wheels, which, by their constant twist, act 
 also by Grinding, (See Chap. II. § 1.) 
 
 2. I have observed that narrow roads are 
 almost always in bad condition, which is to 
 be accounted for from the circumstance of 
 every carriage being obliged to go in the 
 same ruts ; and as each rut is generally only 
 six inches wide, one foot of the road only is 
 worn by the wheels instead of the whole 
 breadth of it ; which would be the case if the 
 road were of a proper width, and if it were 
 well constructed. If a road be laid out, from 
 twenty to thirty feet wide, so flat as that a 
 carriage may stand nearly upright on every 
 part of it, and if moderate care be taken 
 by the Surveyor to prevent the first forma- 
 tion of ruts, such a road will be worn by the 
 wheels nearly alike on every part of it : pro- 
 vided also that the ground on each side, for 
 at least four or five feet, be moderately flat, 
 so as not to excite fear in the drivers of car- 
 riages ; but if there be deep ditches close to 
 the sides of the road, or if the circumjacent 
 
1 12 ESSAY OK [chap. XI. 
 
 land fall off very abruptly to the depth of two 
 or three feet, whereby fear of approaching 
 the edges would operate on the minds of the 
 drivers, every driver will instinctively avoid 
 the danger on either hand ; and a road so 
 circumstanced will, in spite of any care of the 
 Surveyor, inevitably be worn into ruts in the 
 middle. There is a remarkable instance of 
 this kind in a piece of road on Durdham- 
 Down, near Bristol. This road is a cause- 
 way over a piece of soft ground; and al- 
 though it is from twenty to twenty-five feet 
 wide, yet, as the ground falls away abruptly 
 on both sides of it, it has been found impos- 
 sible, for more than twenty years past, to my 
 knowledge, to prevent deep ruts being formed 
 along the middle of it; notwithstanding the 
 Down itself consists of hard limestone ; and 
 the other roads upon the Down are as fine and 
 even as any roads in England. Were this 
 piece of road widened out on each side, in an 
 easy slope, about five feet, by rubbish of any 
 kind, and by the scrapings of the road 
 itself; whereby the instinctive operation of 
 
CHAP. XI.] WHEEL-CARRIAGES. 113 
 
 fear of approaching the sides of the presenj. 
 road would be obviated, that piece of road 
 would be found to wear as fairly as the other 
 roads on the same Down. 
 
 3. If a road be high and convex in the 
 middle, no care of the Surveyor can prevent 
 the formation of a pair of ruts along the 
 ridge of the road ; this, too, from an instinc- 
 tive operation of fear : every driver will take 
 this track, as being the only part of the road 
 where his carriage can stand upright ; and 
 even if it be not so convex as to excite fear, 
 yet the inconvenience of travelling on a slop- 
 ing road will always produce the same effect. 
 
 4. In the use of materials for roads there 
 is seldom much choice ; but Trustees are 
 obliged to use such as the country affords : 
 I have however uniformly observed, in various 
 parts of England, that where limestone is 
 used the roads are the best. And this supe- 
 riority is not in my opinion owing merely to 
 the hardness of this substance, but also to its 
 
114 ESSAY ON [chap. XI. 
 
 adhesive or cementing property : how, other- 
 wise, are we to account for the firmness and 
 soHdity of these roads ? The roads around 
 Bristol that are made of white Hmestone, I 
 mean tlsat rock-hmestone which burns into 
 a white hme, are so firm and compact that 
 they are never affected by tlie most severe 
 frosts ; which proves that they are quite 
 impervious to water. Chalk, being also a 
 limestone, possesses the same cementing qua- 
 lity, and although much softer than the Bristol 
 stone, it may be a good substitute, to mix 
 with harder materials. I was much pleased, 
 the last time I went through Marlborough 
 Forest, at seeing the admirable effect of the 
 miion of chalk and flints : the flints being all 
 reduced to a size scarcely exceeding four 
 ounces in weight each, and a quantity of 
 chalk being mixed w ith them, the road was 
 as smooth, and, as it appeared to me, as 
 hard and compact as the roads on Durdham 
 Down. I am however informed that Uiese 
 roads are affected by frost, because chalk 
 is very absorbent of water : this however I 
 
CHAP. XI.] WHEEL-CARRIAGES. 115 
 
 am persuaded is owing to the chalk being 
 used too abundantly. If used with the bro- 
 ken flints, in the proportion of only one to 
 ten, just enough to form a cementing bed 
 for the flints, I cannot conceiv^e that the 
 quantity of water absorbed would be pro- 
 ductive of injury from the effects of frost. 
 
 That ground-limestone does possess an 
 adhesive or cementing quality is proved by 
 the fact that the scrapings of limestone- 
 roads are frequently used without any ad- 
 mixture, as mortar, not only for building 
 boundary-walls, but also for building houses, 
 for which purpose it is found to answer 
 tolerably well. It therefore becomes a ques- 
 tion, whether the practice of scraping the 
 roads quite clean previous to the laying on of 
 fresh materials, is or is not the best mode of 
 proceeding. It is certain that clean dry 
 stones cannot combine until, by the tritura- 
 tion produced by the action of wheels and 
 of horses' shoes passing over them, tliere 
 is a sufficient quantity of small particles 
 broken off" to form a bed of mortar for 
 
 i2 
 
1 1 6 ESSAY ON [chap. XI. 
 
 the remainder ; and that this is the process 
 is clear to me from a fact I have often 
 observed ; which is, that when broken stones 
 are laid on any part of a road in dry 
 weather ; so long as the weather continues 
 dry, these stones will continue loose, how- 
 ever much they may be pulverized by wear 
 during the dry weather ; but immediately 
 after a storm of rain, the whole that has 
 been much worn becomes firm and solid in 
 a day or two. In other words, the powdered 
 stone, which during the drv season was 
 dust, now becomes mortar, and the whole 
 is cemented or combined together. Hence 
 I am satisfied that, when fresh stones arfr 
 laid upon a road, if a quantity, and not 
 a very small quantity, of the road dirt were 
 thrown back and distributed evenly over the 
 surface, they would immediately become 
 firmly imbedded together ; that they would 
 last much longer, owing to the trituration of 
 them one against another in their rough and 
 dry state being prevented by their being 
 thus protected from the direct action of 
 
CHAP, xl] wheel-carriages. 1 1 7 
 
 wheels and the shoes of liorses : besides 
 which, they would not be so likely to wear 
 into ruts. 
 
 This is not however mere theory; for, 
 having twice served the office of Surveyor 
 of Parochial Highways, I have proved tlie 
 beneficial effects of this practice, and this 
 too with an ordinary red sand-stone. How 
 far, consistently with my theory, it might 
 be advantageous to lay new materials on 
 unscraped roads, I have not proved. 
 
 5. As the wheels of carriages act upon the 
 materials of roads like drug-mills, it may be 
 well to take a lesson from the actual practice 
 of these machines. Having many years ago 
 occasionally worked at a mill of this descrip- 
 tion, which was used for pulverizing the 
 residuum or caput-mortuum of the Nitrous 
 Acid Manufactories, which is a hard sa- 
 line substance, I always found that when 
 I overcharged the mill it would not grind, 
 but the salt formed into a mass, and the 
 
118 ESSAY ON [chap. XI. 
 
 runner passed over it, producing but little 
 comparative effect ; but Avhen I threw small 
 quantities on tlie bed of the mill at a time, 
 so that each piece might come in contact 
 both with the bed of the mill and with the 
 runner, the work proceeded with dispatch : 
 each piece then shared the fate of the piece 
 of brick under my destructive foot, and by 
 precisely a similar process. The same 
 effects I have observed in the laying on of 
 materials on the roads. A covering from 
 four to five inches thick forms a bed or 
 mass, which is proof against the severe crush 
 of heavy wheels ; while in the case of a 
 very thin covering, the stones lying bare 
 upon a hard road, and receiving in this 
 unprotected state the stroke of every wheel 
 that passes over them, like the thin covering 
 on my mill-bed, they are quickly reduced 
 to powder, and disappear. 
 
 On recurring to my juvenile experiment, 
 it must be evident that, had I tried to grind 
 to powder with the twist of my heel a piece 
 
CHAP. XI.] WHEEL-CARRIAGES. 119 
 
 of soft brick that was firmly imbedded in 
 earth, I should have tried iii vain ; because 
 in this case I must also have twisted or 
 loosened the body of earth with which it 
 was surrounded ; which I could not have 
 done : therefore the only effect I could have 
 produced would have been a slight tritura- 
 tion of its 'Surface. This is also the case 
 with heavy wheels : stones in a thick bed 
 are protected from the immediate destructive 
 grind; while stones that are thinly laid on 
 are instantly reduced to powder. 
 
 6. I have generally observed that when 
 a piece of road is covered entirely across 
 with new stones, every carriage follows the 
 track of the first, until a pair of ruts be 
 formed ; and this can be prevented only by 
 the vigilance of the Surveyor, in causing 
 the ruts to be filled up, by the use of iron 
 rakes ; and the labour in drawing heavy 
 carriages over such fresh laid materials is 
 excessive, particularly up hills. Whether 
 or not, by the plan I have suggested, of 
 
120 ESSAY ON [chap. XI. 
 
 spreading dirt over the new stones, the ten- 
 dency of ruts forming A\'ould be entirely pre- 
 vented, I am not certain ; but it is certain that 
 the labour of the horses would be very much 
 reduced in passing over them ; and it it also 
 certain that the stones would not be so liable, 
 nor, I believe, in any degree liable to be 
 displaced by the pressure of the wheels and 
 by the straining of the horses. 
 
 It was formerly the custom, on some of the 
 Bristol roads, to lay only one half of the 
 road at a time. This was, in my opinion, 
 an excellent practice ; because, as every 
 driver of course took the old road, the newly 
 laid road was gradually worn by the wheels 
 on one side of every carriage, while the 
 horses travelled on the old ; and as the old 
 grew worse, every carriage would gradually 
 draw further and further upon the new 
 stones, until the whole was imperceptibly 
 rendered firm and compact; after which, 
 if necessary, a similar process might take 
 place on the other side. By this practice 
 the horses were never obliged to go upon 
 
CHAP. XI.] WHEEL-CARRIAGES. 121 
 
 the new stones unless when two carriages 
 passed each other ; the new stones were 
 very little deranged by the wheels, and the 
 horses' feet ; ruts were never formed ; and 
 the roads were always in good condition. I 
 therefore see no reason why such practice 
 should not generally be adopted. 
 
 FINIS. 
 
 T. J. Manchee, Printer. 
 
I 
 
APPENDIX. 
 
 Remarks on the Friction of Axles, the Elasticittf 
 of the Subsoil, and the Softness of the Surface- 
 matter of Roads, as relating to the Principle 
 of Division of Weight. — On Fat and Oils 
 of different kinds, as applicable to the Axles 
 of Wheels, and to other Machinery. 
 
 As soon as the foregoing sheets were out of 
 the press, I had a few copies put into boards, 
 for distribution among my Friends, with a 
 view of obtaining any hints that might be 
 offered me before the work should be laid 
 before the Public; and some of the following 
 remarks have arisen in consequence of sug- 
 gestions thus produced. 
 
 The Reader will have observed that my 
 arguments in favour of the principle of di- 
 vision are founded on calculations of the 
 powers requisite to draw wheels, carrying 
 certain weights, over stones or other palpable 
 
 K 
 
124 ESSAY ON {appendix. 
 
 obstructions ; winch are seldom likely to be 
 opposed to more tlian one wheel at a time. 
 But it is a fact, which I have j)roved by 
 many years' practice, that three good ordi- 
 nary horses can draw a ton more with four 
 wheels, than they can with two wheels, not 
 only upon smooth level roads, but also up 
 hills. My own Carter has discovered this, 
 contrary to his own prejudice ; and it is his 
 constant declaration that my tico horses, 
 which are strong, active animals, can draw 
 Q5 to 70 hundred- weight gross, with the 
 Waggon, quite as easily as the Cart with 50 
 hundred-weight, even up the hills ; the Wag- 
 gon having narrow wheels, of the heights be- 
 fore mentioned (Chap.V. § 1), and the Cart 
 liaving 6-inch wheels, 4 feet 8 inches high, 
 with iron axles, working also in olive-oil. 
 
 Another circumstance also I will mention. 
 I have a man in my employment, who lately 
 lived two or three years as groom vrith a 
 neighbour of mine, who kept a two-Tvheel 
 one-horse Chaise, and a light Ph£eton ; 
 which latter he also frequently drove with 
 
APPENDIX.] WHEEL-CARRIAGES. 125 
 
 one horse. This man says he always obser- 
 ved that, when his master had been to town, 
 (five miles distant) with the four-wheel 
 Chaise, the horse returned fresher, even 
 though there were three persons in the Car- 
 riage, than when he had drawn the two- 
 wheel Chaise, with his master alone; not- 
 withstanding that the differences of the nett 
 ^veights of the two carriages must have been 
 at least from two to three hundred-weight. 
 This information was not the result of any 
 question from me ; but he mentioned it as a 
 very strange thing, and which he very truly 
 said he " could not make out," as he had 
 " always thought that two wheels followed 
 lighter after a horse than four." 
 
 Here are facts, connected with the prin- 
 ciple of division, which have nothing to do 
 with palpable obstructions ; there being 
 no ruts, nor any stones unless recently 
 laid, between Frenchay and Bristol ; the 
 whole of this road having been what our 
 country-people call Mac-Adam'd. And it 
 is demonstrable that these facts could not 
 K 2 
 
126 ESSAY ON [appendix. 
 
 exist, so far at least as the road is concerned, 
 if the road were a perfect inflexible mathe- 
 matical plane, and if the wheels were per- 
 fect circles. Nor does it appear to me that 
 the inequality of the surface of a good 
 turnpike-road is sufficient to produce these 
 effects. There must, then, I think, be other 
 causes conspiring to produce them. 
 
 At an interview I had with J. L. M^Adam, 
 shortly after he had read the preceding pages, 
 and had in very handsome terms expressed 
 his approbation of what I had written on 
 the subject of Carriages, he asked me if I 
 did not think it was likely that axle-friction 
 might increase in a ratio much greater than 
 that of the weight. When we consider the 
 nature of friction, this appears to me an 
 almost self-evident position. Friction is the 
 rubbing of two bodies, one against the other ; 
 and we know that if a cart or a waggon were 
 set to work with dry axles and boxes, the 
 rough or projecting parts of the one would 
 lay hold on the rough parts of the other, and 
 they would thus tear each other to pieces : 
 
APPENDIX.] WHEEL-CARRIAGES. 127 
 
 great quantities of metallic dust would be 
 produced; and great labour must be ex- 
 erted on the part of the horses to effect it. 
 But it has been found that if any very soft 
 unctuous matter be placed between the metals, 
 in proportion as this destructive contact is 
 thereby prevented, in that proportion is the 
 wear of the metals diminished. This is re- 
 markably the case in my own Waggon. Al- 
 though it has been in use about twelve years, 
 I could not discover, the last time I examined 
 the axles and boxes, that any wear whatever 
 had taken place, whether in the iron of the 
 one or in the brass of the other. Now it is 
 certain that olive-oil will prevent destructive 
 friction, with very considerable weights acting 
 on the sliding-bodies ; but, whenever the 
 weight becomes so excessive upon an axle 
 as that the axle shall drive the oil before it, 
 or press the oil from under it, so that the 
 metals come into absolute contact, the 
 friction must become prodigious; and this 
 increase of friction must be produced in 
 proportion as the weight has this tendency, 
 
128 ESSAY oiv [appendix. 
 
 of displacing the oil aiul of forcing the 
 metals into contact ; and it is therefore 
 clear to me that a double weight might thus 
 produce a tenfold friction. 
 
 Another circumstance has also attracted 
 my notice, since the body of this work was 
 printed ; which is, the Shaking of the Roads. 
 It was first suggested to me by Robert 
 Anstice, of Bridgewater, who is a gentleman 
 of great ingenuity, and of great accuracy in 
 observation. The same fact I see recorded 
 by the Quarterly Reviewers, in their notice of 
 several Works on the subject of Roads, 
 (JMay 1820,) with this very important 
 fact accompanying it, viz. that the mate- 
 rials on the road between Cross and Bridge- 
 water, when compared with similar materials 
 on roads lying upon a hard rock, last in 
 the proportion of seven to live. The fact 
 is so v/ell attested as to leave no doubt with 
 me of its pejfect accuracy. But how or 
 why do these stones last longer on an elastic 
 bed than on a hard rock ? Precisely for the 
 same cause that a stone placed upon a wool- 
 
APPENDIX.] WHEEL-CARRIAGES. 129 
 
 pack would bear a greater pressure before 
 it would be broken, than it would if placed 
 on an anvil. Now the road in question is 
 not over a soft spongy bog, although this 
 level is well known to have been formerly 
 sea : it is a country formed entirely by the 
 deposit of slime from the Bristol Channel; 
 and it is now one of the richest grazing- 
 districts in England, with a sound clay- 
 bottom ; the meadows being every where 
 firm enough to carry oxen of the heaviest 
 weio^hts. 
 
 The knowledge of this shaking has led me 
 to consider the nature of the foundations of 
 roads in general. In this country, the pro- 
 portion of road that lies upon bare rock is 
 very small ; all the rest may, in one general 
 term, be said to lie upon earth. Now earth 
 of every description is absorbent of water. 
 It is so ordered by the Great Author of Na- 
 ture, for the purposes of nature ; to support 
 not only vegetable life, but also the myriads 
 of animated beings that exist under the sur- 
 face of the earth. Water circulates and 
 
130 ESSAY ON [appendix. 
 
 percolates through every pore ; and gases 
 also abound, to a very considerable depth ; 
 consequently the whole surface of the earth 
 may be considered, in some degree, as an 
 elastic body. It is not, therefore, only in the 
 neighbourhood of Bridgewater that the 
 roads are elastic, and that water would be 
 seen to tremble in the ditches at their sides, 
 if ditches full of water existed. We hear 
 the windows of kouses, and the plates and 
 glasses on the shelves, rattle when a carriage 
 passes by, not near Bridgewater only, but in 
 London and Bristol, and every where else. 
 Consequently I consider that all our roads, 
 excepting only those that lie in immediate 
 contact with a hard solid rock, are to a 
 certain extent elastic. But even the surface- 
 matter of the road itself is, generally, taking 
 England throughout, more or less pervious 
 to water, and is therefore more or less elastic 
 or yielding. In proportion, therefore, as this 
 elasticity, or softness, or compressibility, or by 
 whatever term it may be designated, exists 
 either in the subsoil or in the road-matter. 
 
APPENDIX.] WHEEL-CARRIAGES. 131 
 
 or in both, in that proportion will weights 
 sink in passing over such roads. But I 
 have endeavoured to show, in the case of 
 Oxen and Sheep in a soft meadow (Cli. viii. 
 § 8), that the effect of weight increases in a 
 much greater ratio than the weight itself 
 increases. Thus, suppose a Sheep to weigh 
 exactly one-tenth part of an Ox ; the foot of 
 the Ox would tread the turf five inches deep, 
 while the foot of the Sheep would not make 
 an impression exceeding an eighth of an 
 inch in depth, or a fortieth part of the depth 
 of that of the Ox ; but as the hoof of the Ox 
 exceeds that of the Sheep in superficial mea- 
 sure about ten-fold, the Sheep by its tread 
 would not displace more than one part in 
 four hundred of the quantity of earth which 
 the Ox would. 
 
 If, then, it be granted that all earth 
 abounds with both air and water, it follows 
 that such earth is elastic or compressible. 
 But a very great proportion of all the roads 
 ijQ England have a depth of this earth or 
 compressible matter under them. And the 
 
132 ESSAY ON [appendix. 
 
 sut'face-matter of all gravel roads, being 
 also absorbent both of air and water, such 
 roads must necessarily be still ynore compres- 
 sible or yielding.* Consequently all roads, 
 excepting only those that lie in immediate 
 contact with a hard rock, must yield, or 
 bend, upon the principle of elasticity, or 
 must sink in consequence of the looseness of 
 the road-matter; and in many instances both 
 these causes must combine to produce a 
 resistance to every wheel that passes over 
 them : which will be in proportion to the 
 compressing power of such wheel. But it 
 is shown that the compressing powers of 
 weights, acting upon earth, increase in a 
 ratio manifold greater than the weights 
 themselves increase. 
 
 In enumerating the various objects of resist- 
 ance to Wheels (Ch. I. § 3), I have stated 
 the pressure of wheels into the surface-matter 
 
 * May not this account for the fact stated before the 
 Committee of the House of Commons, by the Proprietors 
 of Stage-Coaches, that their horses do not last more 
 than about half as long near London as they do in more 
 remote districts ? 
 
APPENDIX.] WHEEL-CARRIAGES. 133 
 
 of roads as a cause of " prodigious expendi- 
 ture of the strength of horses ;" but I was 
 not tlien aware of what is evidently the fact, 
 that this pressure or sinking is not simply 
 proportioned to the respective weigiits, but 
 that it increases, as already mentioned, in 
 a ratio manifold greater than that of the 
 weights themselves. 
 
 These considerations, with the preceding 
 arguments, afford an explanation, satisfactory 
 at least to myself, of all the circumstances 
 attendant on the Division of Weight. They 
 explain the cause why horses can draw 
 seven or eight hundred- weight each, even 
 upon a smooth road, and up a steep hill, in 
 a Waggon, more than they can in a Cart ; 
 they explain the cause why my neighbour's 
 horse always came home fresher from Bris- 
 tol, with his master's Phaeton, than with the 
 Gig, even though he had several hundred- 
 weight more behind him ; and they tend to 
 establish the assertion of the man who drove 
 the eight-wheel Coach between Bath and 
 Bristol, that it followed very light after the 
 
134 ESSAY ON [appendix, 
 
 horses ; which was only saying, in other 
 words, that they drew it with great ease. 
 
 In wliatever point of view, therefore, we 
 look at the principle of Division, whether it 
 be as regards the drawing weights over 
 stones and other palpable obstructions, or 
 over the little inequalities of the roads ; or as 
 regards the elasticity of the roads, and the 
 sinking of the wheels into the surface-matter 
 of them ; or as it regards the friction of 
 axles ; or as it aiFects the duration of the 
 roads themselves; — it appears to me to be 
 alike important. 
 
 Grease, or fat oils, of any description, will 
 prevent friction; but some are found to an- 
 swer this purpose much better than others. 
 Hard fat is objectionable, on two grounds : 
 first, on account of its toughness, or the diffi- 
 culty with which its parts are separated from 
 each other, which necessarily requires labour 
 to effect ; secondly, its want of fluidity ; 
 whereby the working-part of any machine 
 may often be quite bare, while the fat is 
 deposited in considerable thickness where 
 
APPENDIX.] WHEEL-CARRIAGES. 135 
 
 it is of no use. Fish-oils are frequently 
 used about machinery, because they are 
 bought at a low price. Now, all these oils 
 contain a portion of gelatinous matter ; which 
 may be proved by treating them in a phial 
 with a decoction of oak-bark or of nut-galls. 
 When shaken together, a chemical union is 
 formed between the tannin, or tanning 
 principle of the oak, and the gelatine ; and, 
 if the phial be set by to stand for a few days, 
 the purified oil will rise to the top ; the 
 aqueous fluid, or tan-liquor, will separate at 
 the bottom, and the leathery matter, formed 
 by the union of the tannin and gelatine, will 
 be seen in the middle. This is the case with 
 all the fish-oils, even with pure spermaceti- 
 oil, although not in the degree as with cod 
 and common whale oils. I have found some 
 samples of the latter sorts, when shaken with 
 about an equal quantity of strong bark- 
 liquor, to form into a thick mass like a 
 custard ; and, after it has stood a month, I 
 have not discovered any separation to take 
 place : consequently a very large portion of 
 
136 ESSAY ON [appendix. 
 
 such oils must be jelly. No^v it is found 
 that, when iishroils are used about machi- 
 nery, or about the axjes of wheels, the oil 
 eyaporates, or passes off; and the gelatinous 
 matter remains, adhering to the machinery, 
 like gum : therefore fish-ojls should never be 
 used about machinery of any kind. This 
 deposit of jelly is also observed on harness on 
 which coarse fish-oils are used ; but I have 
 not observed it after using pure sperm ace ti- 
 oiL This seems to be entirely absorbed by 
 the leather, without leaving any deposit of 
 gelatine or gummy matter on the surface of 
 it ; the leather handling smooth and clean, 
 ;and remarkably mellow with its use. Pure 
 olii^e-oil possesses none of the properties that 
 render solid fat or fish-oils objectionable for 
 machinery ; and it is the only substance that 
 I know of which is proper to be applied eitlier 
 ;tQ cart-wheels or to machinery of any kind ; 
 for the former of which purposes I think 
 the best method of applying it is with a 
 small painting-brush ; and there is nothing 
 belter to keep it in, for use, than a common 
 
APPENDIX.] WHEEL-CARRIAGES. 137 
 
 tin pint-porringer, with a cover to keep out 
 the dust ; in which cover should be a notch, 
 to admit the handle of the brush. Three or 
 four ounces of oil, given to the carter at 
 once, will thus last a long time ; as, by the 
 use of the brush, he need not waste a drop 
 of it. 
 
 I should not suppose that the quantity of 
 gelatine in sperm-oil would render it objec- 
 tionable for carriage-wheels ; but I have 
 found it so thin that the boxes would not 
 retain it, and the wheels would not go twenty 
 miles without complaining. I have however 
 found that sperm-oil proves gummy about 
 the works of a steam-engine. I lately gave a 
 phial of very fine sperm-oil, purified by the 
 before-mentioned process, to a watchmaker, 
 thinking it might prove excellent for the 
 pivots of watches ; but it was too thin or 
 too volatile even for that use. He said it 
 was soon gone; but the watches worked 
 remarkably well with it. 
 
T. J. Manchee, Printer, Bristol. 
 
.J*'*?