to be rolled in the course of a period of three or four years, may be arranged for in advance and added to as the work proceeds year by year, the previous annual quantities of material applied to these roads can, by judicious management, be reduced considerably in view of a thorough repair being undertaken within a limited period of time.

In working out this system of concentrating the metalling, due consideration must be given to the requirements of particular roads and certain sections of a road, where circumstances indicate that attention and the application of macadam are necessary to prevent the crust of the road becoming destroyed. It is advisable, not only when rollers are being introduced for the first time, but as rolling operations are extended, to prepare a list of those roads which it may be considered necessary to undertake in the first instance, and those to be dealt with later in rotation.

376. The roads, extending probably many miles, which it is intended to roll during the season following the previous year's supply of metalling, should be repaired by only employing the quantity of material that is just sufficient to maintain a fairly good surface without allowing the road coating to become tracked.

By this means, and when the following year's supply is prepared, a quantity of macadam nearly equal to two years' ordinary allocation is thus reserved until the rolling operations are commenced. This arrangement.

may be extended so that a three or four years' supply may be applied and rolled on any particular road.

As a means to an end, this is the only method which can be followed, unless larger quantities of material can be procured at a cheaper rate. Methods have been described in the chapters on Quarrying and Stonebreaking, by which material can be procured at a small cost.

Undoubtedly a country road can, by careful attention, be kept in good repair with a small quantity of material for a limited period of time, and by allocating a quantity of macadam, to be applied only when the road shows signs of giving way, a large amount of metalling may be reserved and concentrated on roads where found necessary in connection with rolling operations. Adverse weather in the form of alternating frost and thaw, will no doubt injuriously affect certain portions of the road surface, but apart from a trifling expenditure in labour to remedy this, the weak spots can be specially treated previous to or at the same time as the general repairs are effected.

It has already been shown that under the old system of repairing roads by patching and consolidating the coatings by wheel traffic, a layer of macadam one stone thick serves to bear the ordinary traffic without failure of the road surface for a considerable number of years. Any reduction,. therefore, of the annual quantity of metalling applied, as a temporary measure, will not materially affect the strength of the road for a time.

Experience shows that by judiciously arranging the annual allocation of material for repairs, the actual quantity previously used can be reduced by 75 per cent., when rolling operations are to be undertaken the following season, and 50 per cent. in the case of roads which are to be rolled the second year. On these roads which are to have attention during the third season, a quantity of metalling amounting to a 25 per cent. reduction on the former quantity applied will be sufficient for ordinary repairs. It is obvious that by this method of reducing the quantity of road metal, in advance and in regular rotation, a sufficient supply of material will be provided to keep the roller employed in consolidating either large patches of metalling, or wide continuous coatings. It may be well to state here that a reduction in the quantity of metalling used, when spread in continuous stretches and rolled, will give a saving of about 25 per cent. of the total amount formerly applied in patching which was consolidated by vehicular traffic.

377. If the macadam used for repairs is hand-broken, it can be stored in depôts or brought direct from the source of production to the road under repair, care being exercised to avoid unnecessary haulage, which, besides entailing extra cost, does not add in any way to the efficiency of the work.

It happens at times in some counties that a supply of suitable material cannot be obtained in the immediate neighbourhood of the roads to be repaired. This may necessitate the metalling being brought from a considerable distance, even from points beyond the limits of the county where the operations are to be carried out. In such circumstances the cost of maintaining the roads is considerably increased, owing to the high rate paid. for haulage by rail or otherwise, which often amounts to three or four times the initial cost of the macadam at the source of production.

378. Example of the Methods adopted in Arranging for Rolling Operations. Where quarries exist, the rock of which is suitable for producing road metal, and are so conveniently situated in relation to the road where the repairs are to be made that the material can be conveyed by carts or by engines and traction wagons, the following method of arranging the work is usually adopted.

The fixing of the portable stone-breaking machine and all the other accessories being arranged as described in Chapter VI., the points on the road at which the supply of metalling should commence and terminate from the different quarries may best be illustrated by giving an example taken from actual practice.

A road, A B, fig. 120, extending to 5 miles, was repaired by a continuous coating of metal, the width ranging from 14 to 18 feet, while the depth of the macadam varied from one stone thick to 4 inches. The section A d, of the main road A B, had been previously maintained with material of a hard and tough nature, over which a heavy traffic passed. The surface

of the road was considerably worn, which necessitated a coat of metalling 4 inches thick being applied.

The section de was repaired with the same material as the previous section, but the traffic passing over it was of a moderate description; the repairs being effected by scarifying the old surface, bringing it into proper contour, aud applying a coat of metalling one stone thick. The section e B, the wheel traffic over which is considerable, was maintained with a material of a highly siliceous nature, while the surface had become badly cupped, necessitating the coating being scarified and the old material screened to remove the high percentage of small or exhausted material.

This small stuff was laid aside and used afterwards for binding the new metal coating, the thickness to which the macadam was laid being 3 inches between ef, and 4 inches between ƒ B.

The quarries from which the metalling was taken are marked a, b, c in fig. 120.

In deciding from which of the two quarries a and b the material should be taken for repairing the portion of the section from A towards d, the

18 miles0.61----1.27-

18'wide

18 wide 4" thick

Melalling-18 wide-14' wide --·

4"thick one stone H----3" thick

FIG. 120.-Plan showing how to economize haulage from quarries to main road.

rock being of equal quality, the relative distances and the probable expense of working had to be taken into consideration.

The conditions as regards the access to, and the service roads leading from both quarries were very much alike, consequently the cost of haulage per ton-mile did not enter into the question.

The point to be decided was the distance from the points a and b to the .commencement of the section at A. On referring to the measurements on sketch plan, it will be seen that, so far as the mileage is concerned, the quarry a would, for a distance of 3ths of a mile from A towards d, be the preferable one so far from which to procure the material for repairs. The quantity of macadam required for this section A d of the road, to the width

and thickness of coating shown, would be 495 tons, which could be accomplished in about nine days by means of a stone-breaking machine.

Subsequent to breaking this quantity of macadam the stone-breaker would require to be removed to the quarry b, so as to equalize the cost of haulage; but the removal of the plant from the quarry a to that at b, including dismantling and re-erection, would entail an expenditure of 50s. The cost of production therefore would, considering the short period which the plant was required at quarry a, be enhanced by about 11d. per ton, compared with the cost had the breaking machine been set to work in quarry b in the first instance.

The expense of one change or removal was thus avoided, and although the haulage cost more, the total expenditure incurred in repairing the section Ad was less by procuring and breaking all the metalling required from one quarry, instead of, as contemplated at first, dividing the quantity between the two quarries a and b. The cost of removing the plant from one quarry to another is infinitesimal when calculated at so much per ton on a large quantity of material, while it is considerable when only a few days' breaking. is undertaken, by reason of the high proportion of the time required for removing the machinery, to the actual amount of work performed. In other words, the additional cost for breaking by machinery amounts to ląd. per ton when the plant is removed each week, while it is under d. per ton of macadam broken, if a month's work be accomplished before commencing operations in another quarry, compared with a longer period of time.

It will be obvious from these considerations, that the most economical arrangement was to procure the whole material necessary for repairing the section of road mentioned exclusively from the quarry b.

The points and e on the road, being situated exactly at the same distance from the quarries b and c, would, if the conditions were equal, present no difficulty in fixing on the point as that midway along this section, where the cost of haulage from either quarry is equal.

The road from the quarry e is of an undulating nature, however, which involved an increase for haulage of 14d. per tou-mile compared with the cost of haulage from the quarry b. The question presents itself in this way at what point between d and e does the cost of haulage from either quarry become equal? This is simply a matter of calculation. With regard to the section ef, similar conditions as to haulage existed, and the road from the quarry c to B being on a gradual descent, the price per ton-mile for haulage was similar to that from the quarry b, namely 7ąd. As in the preceding case, it is necessary to calculate the cost of conveying the metalling, so that where the materials applied to the road from the two quarries meet, the expenditure for haulage in either case will be the same.

The spreading of the macadam, and therefore the rolling, should be commenced at the part of the road to be repaired which is farthest from the

source of supply; that is, when breaking in quarry b, the repairing of the road should be commenced at the point A, and be continued towards d. The portion of the section de should likewise be arranged for by fixing the point where the operations are to be commenced, and working back to d.

379. Haulage-how arranged.-By arranging the work in this manner the carts or wagons employed in conveying the metalling do not pass the roller, and therefore do not interrupt the work of consolidating the metalling.

In conveying the road metal by team labour direct from the stonebreaking machine, or even when taking it from depôts, tip-carts only should be employed in depositing the macadam on the road, as by so doing the men spreading the material can regulate the supply when being emptied, and so save extra labour in handling.

The macadam is thus placed approximately in position, but all the material should be turned over by shovels so as to equalize the coating. With well-screened metalling less time is necessary to accomplish this than in the case of spreading hand-broken stones or material containing a large proportion of small or of irregular-sized stuff; it is necessary in either case, however, to employ thoroughly experienced men to perform this work, as the future durability of the coating, although rolled, will greatly depend on its having been properly done.

380. The spreading of the metalling, as already stated, is commenced at the point furthest from the quarry, and when a stretch of about 30 lineal yards of road has been coated the rolling is commenced.

To ensure that the proper quantity of macadam is being applied to the road, the area spread each day should be measured. On referring to the weigh-book, the total quantity of material removed from the breaking machine and deposited on the road is ascertained, when it can be easily verified if the proper depth of metalling is being adhered to.

381. Binding Material and Artificial Watering necessary.-Previous to, and during rolling operations, binding material should be prepared from the road sides, if suitable, or brought from the nearest available source, and deposited conveniently on the bermes or in the water-tables on either side, and all the water outlets should be closed.

The rolling, as explained in Chapter VII., is commenced at either side. nearest the water channels; the engine is worked gradually towards the crown of the road, and repeated passages are made in order to set or interlock the macadam, during which process the flat sides of the stones are brought uppermost. After this has been accomplished, and then only, the artificial watering is commenced, when, according to the nature of the material and. weather prevailing, the binding is applied; the new metalling being wet. prevents its being 'licked up' by the roller wheels.

When clean sand is the material made use of for this purpose, it should be spread over the partially rolled metalling evenly and in small quantities as

ន