In Washington still another method is in use for paying for repairs. There a price is paid in bulk for the material used, measured in carts. In 1897 the cost was 95 cents per cubic foot for skimming work, and 52 cents per cubic foot, where the old material was all removed, for wearing surface, and 30 cents per cubic foot for binder. This is probably the best method of all, provided that competent inspectors can be had of the material and method of laying, as in this way the city pays for the actual amount of material used, and consequently the contractor can bid intelligently, knowing that he will be paid for what work he actually does. In this way, as well as by the Buffalo plan, the amount of repairs can be ordered by the city and carried out without any friction on the part of the contractor. By the Omaha and Cincinnati methods disputes are liable to and often do arise as to the exact amount of surface to be relaid. In these four cities more definite figures have been obtained as to the actual cost to the city for repairs than in any other places in the United States.

Table No. 63 shows the average annual cost per yard for repairs after the expiration of guarantee at the end of different periods. That is, all pavements after they have been out of guarantee from one to seventeen years had cost on an average the

TABLE NO. 64.

SHOWING THE AVERAGE COST PER YARD FOR EACH YEAR AFTER
GUARANTEE HAS EXPIRED.

amount opposite the year out of guarantee, while Table No. 64 shows the average cost per yard for each year after the guarantee has expired, the figures representing the average of all pavements during the first, second, and third years out of guarantee respectively, being made up for Washington and Buffalo from 1897 reports, and by personal inquiry from Cincinnati and Omaha. The original guarantee in every case was five years, except upon streets paved in Buffalo in 1884, when it was eight years. It will be seen in the Omaha figures that the repairs for the eleventh year out of guarantee cost only 3 cents, while for all other years they cost 8 cents. This figure of 3 cents referred to one street only, but it was the first street paved with asphalt west of Chicago, if not west of Ohio. It is possible, too, that the street might have been left in such good condition at the end of this guarantee that it required but little repairs the following year, as it is impossible for any one to tell by examination of the asphalt what its economical condition. is as regards repairs without the entire history of the pavement and its maintenance cost.

The average cost per yard of all asphalt maintained in Buffalo

has been: for 1895, $0.067; 1896, $0.0439; 1897, $0.0480; and 1898, $0.0288.

The Chief Engineer of Buffalo, in his report for the year ending December 31, 1898, submitted a list of asphalt streets that he recommended be repaved, as they had cost on an average from $0.0558 to $0.30 per yard per year for repairs. Only 2 per cent of the entire pavement under maintenance required repairing in 1898, as against 5 per cent in 1895.

In Rochester, N. Y., the cost of maintaining 300,000 square yards of asphalt pavement in 1898 was $0.004 per yard.

In some of the Denver, Colo., specifications a proposition was made for making a contract for repairs for an additional ten years after the expiration of the guarantee period, at a cost not to exceed 10 cents per yard per year. In recent specifications of Newark, N. J., the city agreed to pay the contractor 5 cents per yard per year for the ten years following the five-year guarantee.

European pavements have cost considerably more than those of the United States. This is attributable principally to the increased traffic. The average cost of maintenance per square yard in Paris for 1893 was 37 cents. In Berlin it was 10 cents per yard per year for a period of fifteen years after the guarantee period had expired, and on railroad streets 15 cents for space between tracks and for a distance of 27 inches outside. In London in 1882 the average cost of twenty-eight streets was 21 cents per yard. In Glasgow a sinking fund of 10 per cent is provided in the case of asphalt for maintenance and repairs. In Leith, Scotland, one asphalt street cost 5 cents per yard per year for fifteen years following the third year after being laid.

Noiseless Manhole Covers.

On streets paved with asphalt, where sewer manholes occur at frequent intervals, complaints have often been made of the noise caused by the wheels of vehicles running from the asphalt over the iron manhole-cover. To obviate this trouble a cover shown in Fig. 15 has been used successfully in Brooklyn.

The covers are taken to the contractors' yard and then filled with the asphalt mixture, when they are distributed on the different streets as may be desired.

It is difficult to make an estimate of the cost of a sheet-asphalt pavement.

The price of the different kinds of material varies, as well as the quantities used per square yard.

The tools and machinery used for laying and mixing are ex

pensive and involve the expenditure of a large sum of money, the interest on which and the depreciation of the plant varying the price per yard according to the amount of pavement laid in any one year.

There are also many other charges, such as labor, superintendence, etc., that could not be accurately determined without access to the books of the contractor.

Assuming a square yard of wearing surface to weigh 90 pounds. per inch of depth, and knowing the percentage of bitumen required in the pavement, as well as the amount contained in the asphalt, the pounds of asphalt per square yard of surface can be easily calculated. Its quantity must vary greatly when asphalts containing from 55 to 90 per cent of bitumen are used.

Of 80 per cent asphaltic cement 20 pounds will lay a square yard of wearing surface 2 inches thick, which will analyze about 9 per cent bitumen; always remembering that if petroleum is used for a flux, practically all of it will be soluble in carbon bisulphide and consequently will rank as bitumen.

In Brooklyn, N. Y., asphalt pavements consisting of 2 inches of wearing surface and 1 inch of binder were laid for 80 cents per square yard.

This price, however, was the result of keen competition and cannot be taken as a guide to the actual cost.

Cost of Asphalt.

In a trade pamphlet issued a few years ago by the Standard Asphalt Co., California asphalt containing 90 per cent bitumen was offered in New York for $32 per ton shipped by rail, and $26.50 via Cape Horn on sailing vessels. The cost was determined by a fixed price of $17.50 per ton at Asphalto, Cal.

Asphalt from Los Angeles, Cal., was offered in New York in 1898 for $26 per ton containing 90 per cent bitumen. And it should be remembered that in purchasing any asphalt the amount of contained bitumen should always be stated, as this ingredient represents the valuable portion of the material.

The market price of refined Trinidad asphalt in the New York market is about $30 per ton.