said work and employ others to do the remainder. In case of such suspension the commissioners shall have the further right, at their election, to take possession of, without legal process, and to use such reasonable force and means as may be necessary to take possession of the plant and equipment used by the contractor upon the work and to use the same in doing the work, without compensation for such use, license so to do being hereby given by the contractor, and the contractor hereby forever releases and discharges the commissioners and the District of Columbia from any and all damages or injuries which may be sustained, suffered, or claimed by reason of such possession and use of said plant and equipment.

All cost, damage, expense, and money expended or incurred by the commissioners of the District of Columbia by reason of such failure of the contractor and the cost of completing said work shall be charged against and paid by the contractor, and any money due or to become due him under the contract shall be applied toward the payment thereof.

44. Nuisance. All work done under any contract must be performed in such a manner as, in the opinion of the commissioners, will not create a nuisance nor be injurious to public health.

45. Commissioners.-Wherever the word "commissioners" is used, it is understood to mean the Commissioners of the District of Columbia.

46. Supplementary service.-If any contractor for the collection and removal of any class of material described in paragraph 1 of these specifications, fails, upon request by the commissioners, to provide in full the schedule collection service as required by the contract, the commissioners may, after one week's notice in writing to said contractor, cause to be instituted a supplementary collection service by vehicles employed under their own direction and may charge the cost of such additional service to the said contractor; and the amount of such cost will be deducted from any moneys due or to become due said contractor, and retained by the District or paid to the person or persons employed by the commissioners to do such work.

47. Removal of night soil from temporary construction work.-The contractor for the collection and removal of night soil will be required, and said contractor hereby agrees to collect and to remove within 48 hours after notice to do so, all such night soil as may accumulate in regulation privies established within the District of Columbia by contractors engaged on construction work; and said contractor for the collection and removal of such night soil hereby agrees to charge the person requesting such collection and removal at the rate of not to exceed $1 per barrel of 48 gallons capacity.

HAULING ASHES AND REFUSE FROM BUILDINGS UNDER CONTROL OF THE COMMISSIONERS.

48. Work to be done.-The work to be done consists of hauling all ashes and refuse from the following buildings under the control of the commissioners, viz, public-school buildings, houses of fire apparatus companies, police stations, District Building, municipal lodging house, police court, Home for ex-Union Soldiers and Sailors, and from any other District institutions or buildings that the commissioners may order, the same to be disposed of as required by regulations of the District of Columbia. Ashes may become the property of the contractor or, at his option, may be deposited on the dumps designated from time to time by the commissioners and in accordance with their direction. Paper and other light refuse must be removed in sacks or bags tightly tied, or otherwise secured, so that none of the contents can escape in loading or in transportation, and such refuse may become the property of the contractor or may, at his option, be delivered to the contractor for the disposal of miscellaneous refuse at the point or points designated by said latter contractor, and approved by the commissioners.

49. Carts or wagons.-Bidders for hauling ashes and refuse from buildings under the control of the commissioners must state specifically what facilities they have for doing the work, and all carts or wagons used on the work must have tight bodies and have a capacity of 1 cubic yard or exact multiple otheref. The carts or wagons are to be covered while going to the dump, and no vehicle is to be used unless measured by the sealer of weights and measures of the District, who will mark in a conspicuous place on the body the capacity of each when filled with a "well rounded off" load. 50. Quantity-Nothing in this contract shall be so construed as to prevent the District of Columbia from hauling such quantities of such ashes and refuse, or from permitting others to remove so much of the same without cost to the District, as the commissioners may desire. The removal by the contractor of less than a full load will not be permitted. Rubbish and ashes must be hauled separately and must not be mixed.

51. Payments.-Payments for hauling ashes and refuse from buildings under the control of the commissioners will be made monthly for all jobs of work which shall have been completed during the previous month, as required by the contract. Bills

must be made in triplicate on forms to be furnished by the commissioners and presented monthly, together with the receipts, to the auditor, District of Columbia, District Building.

52. Receipts. The contractor for the hauling of ashes and refuse from buildings under the control of the commissioners will be required to take receipts for all ashes and refuse removed by him.

53. Time of collection.-Collections of ashes and refuse from the buildings referred to in paragraph 48 of these specifications must be made within 48 hours after notice from the superintendent of street cleaning, and failure to make such collections will render the contractor liable to the provision of this contract providing for failure and for liquidated damages. (See pars. 37 and 43.)

REPORT OF INSPECTOR OF ASPHALTS AND CEMENTS.

WASHINGTON, September 4, 1912. CAPTAIN: I have the honor to submit the following report of the operations of this office during the fiscal year ending June 30, 1912, summarized in the following tables: Total number of samples tested.

Asphalts:

Bermudez..

California..

Mexican...

5143

ASPHALTS.

Tests of samples of asphalt used in the laying of pavements for the District of Columbia showed the following percentage of bitumen soluble in carbon bisulphide: From Cranfield Paving Co., 5 samples Bermudez, refined, representing 3,020 tons, 94.5 per cent; from Washington Asphalt Block & Tile Co., 1 sample, Lake Trinidad, crude, representing 1,20C tons, 53.4 per cent (after refining).

ASPHALT CEMENTS.

Penetration results of asphalt binder and topping used by the paving companies.

Analysis of 16 samples taken from the Cranford Paving Co. showed an average of 3.9 per cent bitumen soluble in carbon bisulphide.

BINDER STONE.

During the year there were examined 91 samples of binder stone used by contractor (Cranford Paving Co.) in laying asphalt streets, representing 91,000 cubic yards, with no rejections.

ASPHALT SURFACE MIXTURES.

During the year 206 samples of Bermudez asphalt from the plant of the Cranford Paving Co. were submitted for examination and analysis. The maximum, minimum, and average per cent bitumen contained, and the average mesh composition of sand used is as follows: Highest, 11.4; lowest, 9.3; average, 10.4.

This material is used as a filler to reduce the percentage of voids in the sand used in the asphalt surface mixture. There were examined 22 samples (550 tons) from Cranford Paving Co., all of which passed the required degree of fineness, i. e., all to pass 30 and not less than 85 per cent to pass 100-mesh sieve.

62258°-d o 1912-VOL 2- -6

SAND FOR USE IN SURFACE MIXTURES.

Of this material 285 scows equalling 39,070 cubic yards were inspected, of which 25,570 were rejected on account of coarseness and excessive percentage of mud.

PETROLEUM RESIDUUM.

All residuum used during the year by the contractors in the preparation of asphalt cements was the product of the Standard Oil Co. A total of 30 samples were submitted by the contractors for test and examination, which showed the following:

Cranford Paving Co. (17 samples).

Washington Asphalt Block & Tile Co. (13 samples)......

Pounds.

850,000

495, 528

One lot, 50,000 pounds, at the plant of the Washington Asphalt Block & Tile Co. were rejected; contained water.

During the year there were manufactured by the Washington Asphalt Block & Tile Co., of this city, about 1,234,512 paving blocks. They were used in the paving of various streets, avenues, and alleys, approach to, and the plaza of the Union Station. These blocks were manufactured of Trinidad Lake asphalt, fluxed with petroleum residuum and a mineral aggregate composed of Potomac granite and limestone. Following is a table showing average results of tests of material used in their manufacture: Average results of tests of asphalt cement and mineral aggregate used in the manufacture of asphalt blocks.

During the year there were laid by the Cranford Paving Co., under contract, about 22,156 square yards of asphalt macadam. The roadbed was prepared by the District and consisted of a first layer of trap rock ranging in size from 24 inches to dust laid to a thickness of 5 inches and rolled with a 10-ton steam roller until thoroughly compact.

Upon this roadbed hot asphalt (Bermudez) macadam mixture was spread. This mixture consisted of 2 parts trap rock crushed to a size from 1 inch to dust and 1 part sand, to which was added about 5 per cent limestone dust. The crushed stone and sand were heated to a temperature of about 250° F., the limestone dust being added in a cool state to the hot mixture, conveyed to an asphalt mixer, and thoroughly mixed. Hot asphalt cement was then added and the whole thoroughly mixed for a period of about five minutes; it was then hauled from the paving plant to the site of the work, spread over the road bed to a thickness of 3 inches, then rolled with 5 and 10 ton steam rollers until thoroughly compact. Over this surface was then spread a thin coating of hot asphaltic cement for the purpose of filling voids. A thin coating of trap rock screenings three-eighths-inch to dust was then spread on the surface as a top and final coating and rolled with a 10-ton steam roller.

Following is a table showing average results of laboratory tests of asphaltic cement and the mineral aggregate used in the preparation of the asphalt macadam: Asphalt cement (Bermudez) soluble in carbon bisulphide.......

Penetration:

per cent..

98.4

At 32° F., 200 grams, 5 séconds

10.0

At 77° F., 100 grams, 5 seconds

62.0

At 115° F., 50 grams, 5 seconds.

per minute).

Brittleness at 32° F. (in centimeters, drop of 25 grams weight).

Ductility at 77° F. (length of stretch in centimeters at the rate of 5 centimeters.

Loss by volatilization, at 300° F., 18 hours...

220.0

34.0

20.0

....do....

45.0

None.

MACADAM MIXTURE.

Bitumen soluble in carbon bisulphide (not including flush coat)...per cent..

MINERAL AGGREGATE, MESH COMPOSITION.

Barrels inspected and the average results of tests on same Portland cement.

In the testing of cement, samples are taken from 10 barrels of each 100-barrel lot and tested individually, The 9,203 samples tested represent 92,050 barrels, of which 1,050 were rejected.