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; ° r ^ an d strong foundation, it should be borne in mind| ar e structures that have to sustain great weights,W f 0 jj ent percussion; the same rules, therefore, ought toVtu. with them as are followed with regard to other^«rne S in A road will never be of long duration, nor ata , e >n a satisfactory condition, which lias not a firm^cted Stant ‘ a l foundation. But not only is its durability°tlie r D . Utl( ler such circumstances, it has disadvantages in'fay, j| nt . s e fiually important and essential to a good road-®‘der j( 8 esi des the durability of a structure, we have to con-°r . Economy, and its adaptation to the special purposea good r U -* S ' nten ded. Now, the object to be attained by'oadjgjt ° a<a >s the conveyance or transport of goods in the° Cc,)r t'in» n ^ most economical manner, so that the constantly-Ca ° „ ex P ense of transit ought to be taken into evento ad j. ® bi eonsideration than the original outlay upon the^pea Se e » We want goods to be conveyed at as small an1 6 for tT ^ oss '* 3 ^ e- Now, the largest item in the expendi-

conveyance of goods consists in the expense ofou nt ' " r employed ; and as much as we can reduce the

^Power

^ewj Se °^ 'ids power, by so much do we reduce the expensePowe ■According to all experience, as well as science,F re< l u ii'ed to draw a carriage, or any body, over a0 fo'aw tT e ‘ ast ’ c surface, is much greater than that required^a 0ri . le same over a hard unyielding surface ; and the"foe n=, • Pia>n—there is not so much friction in the latter

as

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,0 ai\vay o\ e conv eyance is not so great as on a yieldingresistance,” says Professor Leslie, “ whichd(ls ; • Cca sions, partakes of the nature of the resistance of

t 'he 1 , Co f s >sts of the consumption of the moving-force, ore °H and°ti' e 8 iadour, occasioned by the soft surface of thea foat a l e continually depressing of the spongy and elasticf > ge 'de road. In fact, on a yielding roadway, theh ° r i as u, r ,' va Sgon has to be drawn over a series of hillocks,N j ‘ he l°ad

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passes over, it depresses that portion of the

Pr its t te ’^ l )eneat l 1 an< l has before it, to be passedon Ss : tl tUl n ’ a P ort ' on which has not yet undergone thisth r<) a<ls Q i e ® OIU parison between the tractive power employed• ®® ren t elasticities, has been well illustrated—c 611 a tu i' Vor y ball set in motion with a certain velocity. , lke y carpet, will suffer a visible relaxation of its8 ''W if 1 '^e same impelling force it will advance

v>*‘ , oakI 0 n lle , d over a superfine cloth ; still farther overSty 6tl Pranks ; and it will scarcely seem to abate itst}) Vf^ 1 ' a sheet of fine ice.”

in hard ® reater tractive power being required in elasticer ' rtl ent r ° a d s has been proved beyond a doubt, by ther^ated 8 made by Sir John Macneil, by his machinetij'.'cse “'‘ms purpose.

and * 8 'n e P eri ments uniformly show, that the force of trac-'^6li' lar dnel ei ^ Case l n an exact proportion to the strengthg ‘Sad e t , S op a road. The following are the results on aof ’ 8 u3ib ' avement: —The power required to draw a wag-tl,^ r '-at •’ on a road made with 6 inches of broken stonesa t ^° r tn 0 p ness > laid on a foundation of large stones set in

^tlf.Ndea 'Hi'

Pavement, the power required is 461bs.; onth e nn a thick coating of broken stone, laid on

R-'ck » p0w « required is 65lbs. ; and on a road made withS it a ^ at,n g of gravel, the power required is 147 lbs. .^ tr <L Pears that the results of actual experiments fullyv>Sir j./ 1 with those deduced from the laws of science.

in -’ c- " ---

tl of A’ “* his examination before a Committee of theU C °mm°ns in 1836, says, “The great advantage ofi! tll6 ir Jft peari "8 by the machine is certainly in proportionS' If ? hdlt y and their strength, and their want of yield-' could be a perfectly solid mass of stone or metal,

the least resistance would be presented ; that is shownboth on stone tramways and on metal tramwavs, and metalrails.”

The foundation should be composed either of a roughpaving of large stones, or of a sufficient bed of concrete,the former being the practice of Mr. Telford, and the latter ofmany engineers of the present day ; the selection of eitherof these materials will depend upon their economy in variousplaces ; whichever is most accessible, may be safely used ;but whatever material be used, it is necessary that the sub-stratum should be of uniform strength and solidity over theentire surface, otherwise, after the pavement has been laid,the weaker parts will give way, while the stronger maintaintheir position, and so the surface of the road becomes brokenand uneven, rugged, and full of hollows ? for this reason weprefer the use of concrete, which offers greater securityagainst this defect than foundations made of large stones orrubble, though in many roads even concrete is not sufficiententirely to prevent it. We are inclined to think that thevalue of concrete for this purpose has not been fairly tested,for the work, especially in London roads, is usually gotthrough in so hurried a manner as not to allow a sufficienttime for setting : we imagine, that with a somewhat thickerbed of concrete, the materials of which have been properlymixed, and allowed a sufficient time to set before the metal-ling is put on, we should be enabled to construct roads suffi-ciently firm to bear the extraordinary wear and tear of - Lon-don traffic, and that, too, at a less cost than is expended onthe present roadways. We are aware that there are manydisadvantages to contend with in London roads ; that theyare continually being pulled up, and thereby destroyed, forworks connected with water, gas, or sewers, and that thisacts as a great discouragement to the construction of goodroads. That any necessity of this nature should be allowedto exist is much to be lamented, but we feel confident thatsuch practices might be restricted to a very considerableextent, without doing any injury to the public convenience.The concrete foundation should be slightly curved, fallingfrom the centre towards both sides, which form will assist todrain it, and also to give the proper form to the surface ofthe roadway. It is necessary that this lower surface shouldbe properly drained, otherwise the water will lie there, anddestroy the road. If the concrete were laid 18 inches thick,we should not deem the extra expense ill laid out for a goodroad. With respect to the other kind of foundations, Mr.Parnell says—“ In streets where the traffic is not very great,the foundation should be made in the following manner:—A bed should be formed, with a convexity of 2 inches to 10feet, so as to admit of 12 inches of broken stone being laidupon it: these should be put on in layers of 4 inches at atime. After the first layer is put on, the street should bekept open for carriages to pass over it. When the firstlayer has become firm and consolidated, then another layerof 4 inches should be laid on, and worked in as before, carebeing taken to rake the ruts and tracks of the wheels ofcarriages, so that the surface may become smooth and con-solidated. The same process should be repeated with thethird layer of stones, by which means a solid and firm foun-dation will be established, of 12 inches in thickness, for thedressed paving-stones to lie upon.” Such directions deservegreater attention than we fear they usually receive ; in allcases, let your foundation be secure before you lay yourroadway.

Various kinds of materials are used for the purposeof forming the upper coat of the road, and amongstthose most frequently employed may be mentioned brokenGuernsey granite, flints, gravel, and cubes of granite of