GRADING AND DRAINAGE.

As the grading of the avenue had apparently been originally regulated in reference to each individual square, without much regard to the adjacent ones, it was not an easy matter to establish satisfactory grades for the street as a whole; and as the pavements selected required a comparatively flat surface, it was necessary to remove throughout almost the entire length a large amount of earth from the center of the street, and to lower the railroad-tracks, and at several points to raise the curbstones a few inches-at one point as much as 133 inches-and relay the corresponding sidewalks. It was also necessary in many cases to increase the inlets to the sewer-basins, to insure the discharge of the surface-water in heavy rains, and in some instances to change the positions of these inlets to adapt them to the new grades. The man-hole and stop-cock boxes for water, of which there are about 37 through the body of the pavement, had to be raised and lowered to conform to the new grades. Proposals were invited for the work from several parties engaged in such business, and the offer of Mr. John J. Burrows, a copy of which is appended, marked "E," was accepted. The resulting grades are pretty satisfactory, and the drainage is believed to be an improvement on that hitherto existing.

STREET-RAILROADS.

By the third section of the act, the Washington and Georgetown Railroad Company is restricted in the paving between the exterior rails of its tracks to the use of cobble-stones or Belgian blocks, as the commissioners shall direct. The commission designated the latter, in blocks not less than 24 by 8 inches by 5 to 6 inches deep.

The road has been paved accordingly from Fifteenth street to Sixth street with the North River bluestone, and thence to the Capitol grounds with Richmond granite. Section 7 of the act provides that where street-railroads cross the avenue, the pavement between their tracks shall conform to the kind of pavement used on the avenue; and the roads crossing at Fourteenth and Ninth streets are to be paved accordingly. The road crossing the avenue at Seventh street belongs to the Washington and Georgetown Railroad, and is claimed to be subject only to the requirements of section 3. In view of the doubt existing as to the intention of the law in this particular, and as a majority of the commission considered a pavement of Belgian blocks to be the most appropriate for the tracks at a point like this, where it is subject to a very heavy traffic, far exceeding that at any other point on the avenue, the railroad company were authorized to pave this crossing in the same manner as prescribed for the main portion of their road.

CHARACTER OF PAVEMENT SELECTED.

It has been already stated that the stone-block pavement and the Telford roadway were excluded by the commission. While stone blocks may be essential to the durability of a roadway constantly crowded with heavy traffic, and while they possess the advantage of affording a comparatively secure footing for animals, they are so very noisy and so difficult to keep clean as to render them undesirable on a street like Pennsylvania avenue, which is mainly used for pleasure-driving and for traffic in comparatively light vehicles. The Telford roadway, while affording a smooth and pleasant surface for driving when kept in good

condition, needs a constant and daily attention in the way of repairs, and frequent sprinkling in dry weather, which it would be impossible to secure with any certainty. Moreover, the muddy surface in wet weather is always considered an objection to it in this country, except for suburban roads.

It is believed, also, that neither of these kinds of pavements would have met the wishes of the citizens of Washington, or of Congress.

It has also been mentioned that concrete pavements in which the prod ucts of coal-tar, as the cementing material, largely predominated in the top or wearing surface were ruled out. It was the belief of the commission that while such pavements, if well constructed, were excellent when first laid, they were subject to rapid deterioration within a few years, owing to the escape of the volatile oils they contain, and this opinion seemed to be fully sustained by the experience had with such pavements in Washington, which have needed resurfacing in three or four years.

Experience has shown that pavements in which the cementing ingre dient is asphalt, which does not contain the volatile matters found in the coal-tar products, are not subject to the same rapid deterioration, and that they will last when well laid, without sensible wear, for a great many years. If a continuous-surface pavement was, therefore, to be selected as one best suited for the avenue, it was the opinion of the commission that the kind in which asphalt alone forms the cementing ingredient should be chosen. Of these were selected the pavement as laid by the Grahamite and Trinidad Asphalt Pavement Company, and that of the North American Neuchatel Rock Paving Company. Both are laid on a continuous bed of hydraulic concrete, not less than eight inches thick. The top layer or wearing-surface of the former is an arti ficial mixture of sand with about 20 per cent. of refined asphalt; and the latter is of the Neuchatel rock, from Switzerland, which is a natural stone impregnated with asphalt.

The former has been tried on several blocks in the city of New York, where it has been subjected to travel from three to four years without sensible wear. The piece on Fifth avenue, in New York, opposite to the Worth monument, between Twenty-fourth and Twenty-fifth streets, was laid in June, 1873, and has experienced a trial far beyond that which it will be subject to bere in twice that length of time. A piece cut out in August last, and now in possession of the commission as a standard of the quality of the pavement to be laid on the avenue, showed no appre ciable signs of wear or other deterioration.

The pavement of Neuchatel rock has long been used in Europe, espe cially in the cities of Paris and London, and bears the character of a first-class pavement of its kind. In view of the long experience had with this pavement abroad, the commission was not disposed to exclude it from their choice if it could be contracted for at the same price per yard as the Grahamite. By dividing the contract, an earlier completion of the work was secured, and an opportunity afforded for definitely de termining the relative qualities of the two-a question which the com mission found itself unable to decide, as is shown by its considering both as fulfilling the condition of being the "best pavements" required by the act. Continuous-surface pavements, whether containing asphalt, the products of coal-tar, or a mixture of the two, as their cementing medium, depend for their quality upon the proportions of the ingredients used, the amount of heat employed in the preparation, and thorough work in laying. If too great heat be applied, the mixture loses its ce menting properties, and the pavement becomes little better than a mass of loose powder. This cannot generally be determined during either

process of mixing or laying, but is soon developed by use. Where this happens, the defective portion is removed and new material substituted therefor. A large percentage of the top surface under each contract has been condemned by the commission, and has been or will be relaid.

AMOUNT OF WORK DONE.

The Grabamite Company have finished the pavement on the north side of the avenue between Fifteenth and the east side of Sixth street, and nearly all of the hydraulic-concrete foundation on the south side. Four or five good working days will suffice for the completion of the foundation. This would have been put down before this time but for the freezing weather which has necessitated the stoppage of the work while the low temperature continued.

The Neuchatel Company have completed the pavement on both sides of the avenue from the east side of Sixth street to near First street, and require only two or three days of good weather to enable them to finish their contract.

PROBABLE TIME OF COMPLETION.

As but little remains to be done under the contract with the Neuchatel Company, it is not supposed that the weather can prevent its completion before the time fixed by law. As regards the much larger amount of work remaining unfinished under the contract with the Grahamite Company, its completion by the 15th of January can scarcely be expected, and believing that the company has prosecuted their work with due diligence, the commission recommend that the requirement of the law for its completion by that day be either repealed or that the time be extended to February 15, 1877. Respectfully submitted.

H. G. WRIGHT,

Bvt. Maj. Gen., U. S. A.,
Q. A. GILLMORE,
Bvt. Maj. Gen., U. S. A.,
EDWARD CLARK,
Commissioners.

A.-Proposals.

PROPOSALS FOR PAVING.

OFFICE OF COMMISSION FOR PAVING PENNSYLVANIA AVENUE,

Washington, D. C., July 29, 1876.

Sealed proposals will be received at the office of the Architect of United States Capitol until 12 m. on Tuesday, the 8th day of August, 1876, for repaving Pennsylvania avenue, in this city, between the Capitol and the Treasury building, under the provisions of the act of Congress approved July 19, 1876.

The proposals must be accompanied by detailed specifications giving the depth of the proposed pavement, the method to be followed in laying it, and the nature and proportion of its constituent parts.

Bidders for stone-block pavements will specify the character of the foundation, the sizes of the blocks, and the quarries from which they are to be supplied.

Proposals must be made by the superficial yard, which will include the cost of readjusting the curb-stones wherever necessary to secure a straight line on the face and top, and the cost of removing the present pavement and delivering the same to the Commissioners of the District of Columbia, as provided in the act.

The proposals for all other than block pavements must also include the cost of lowering the crown of the street wherever the commissioners shall consider it necessary in order to establish more gentle slopes from crown to the gutters. Proposals for this class of pavement should give separate estimates for different thicknesses, from ten inches up to thirteen inches, and must also give the thickness of the surface or wearing layer.

All proposals must include the cost of keeping the pavement in good repair for a term of three years from the completion of the contract.

No proposal will be entertained unless accompanied by a bond in the sum of $100,000, signed by two responsible bondsmen and approved as to sufficiency by a judge or cleri of the United States court or a United States district attorney, that the bidder will the work be awarded to him, enter into a contract within ten days after the awards made, and construct the pavement according to the terms of the contract and specications.

Payments will be made on account from time to time as the work progresses and v the funds become available. Upon final settlement, ten per cent. of the contract-priz will be retained as an additional security and guarantee-fund to keep the pavement good repair for the term of three years, which ten per centum will be invested in the bonds of the United States and the interest thereon paid to the contractor. Upon a plication by letter, a copy of the act of Congress authorizing this work can be obtained of Edward Clark, esq., member of the commission, at the office of the Architect of the United States Capitol, Washington, D. C.

H. G. WRIGHT,

But. Maj. Gen., U. §. A. Q. A. GILLMORE,

Bvt. Maj. Gen., U. 8. d EDWARD CLARK,

Commissioners.

B.

11

13 Gantz, Chowley & Co
W. H. Allen.

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18

23 Charles Guidet..