amount on the palm, which will be soiled by any clay or loam present.)

Paragraph 9. Cement.-Unless otherwise specified all cement shall be of the best quality of natural cement, and when tested neat in briquettes (Am. Soc. C. E. standard) shall show a tensile strength of at least 75 pounds after 1 hour in air and 23 hours in water and of at least 150 pounds after I day in air and 6 days in water. Cement for brick masonry or pipe-joints, when these are laid in wet ground, shall be quick-setting and show a tensile strength of at least 100 pounds per square inch after 24 hours. Pats of neat cement made on glass and brought to a thin edge shall show no checks after setting in boiling water.

When specified Portland cement shall be used. This shall show a tensile strength of at least 400 pounds per square inch in a 7-day test made as above, and pats of the same shall show no checking. The cement mixed neat and stiff into patsinch thick shall develop "initial" set in not less than 20 minutes and "hard" set in not less than 45 minutes after mixing, except in the case of quick-setting cement to be used as specified above.

The engineer shall be allowed to test all cement and notice of its receipt by the contractor must be made to the engineer at least 48 hours in advance of its use upon the work. Any cement not satisfactory to him shall be at once removed from the work.

Paragraph 10. Packing.-Packing may consist of flax, jute, oakum, or hemp, clean and with long fibres loosely twisted into strands.

Paragraph 11. Timber.-All timber and planking used in cradles, platforms, and foundations shall be of spruce, or timber equally as good, straight, sound, free from sap, shakes, large, loose, or decayed knots, worm-holes, or other imperfections which may impair its strength or durability. Piles

shall be of sound, straight, live spruce or yellow-pine timber, of lengths specified by the engineer for each locality. They shall be not less than 6 inches in diameter at the smaller end. The bark shall be removed in all cases.

ART. 52. EXCAVATION.

All ma

Paragraph 12. Classification of Materials. terials excavated shall be classified as either earth or rock. No material shall be classified as rock which cannot be removed more cheaply by drilling and blasting than by picking, except that any boulder measuring cubic yard or more shall be so classified, whether blasted or removed bodily; but such boulder shall not be returned to the trench without being first broken up.

Paragraph 13. Excavation of Trench.-The trench shall be excavated along the line designated by the engineer and to the depth necessary for laying the sewer or sub-drain at the grade given by him. In the case of pipe sewers it shall be I foot wider at the bottom than the outside diameter of the pipe, and for brick sewers as wide as the greatest external horizontal width of the structure to be placed therein, without any undercutting of the banks. Where, in the opinion of the engineer, the original earth is sufficiently compact and solid for the foundation of the work the contractor shall excavate the bottom of the trench to conform to the external form and dimensions of the invert or foundation as ordered. For pipe sewers the bottom of the trench under each bell shall be so hollowed out as to allow the body of the pipe to have a bearing throughout on the trench bottom and permit of making the joint. In case a trench be excavated at any place, excepting at joints, below the proper grade it shall be refilled to grade with sand or loam thoroughly rammed, without

extra compensation unless the extra excavation was ordered by the engineer.

The material excavated shall be laid compactly on the side of the trench and kept trimmed up so as to be of as little inconvenience as possible to the travelling public and to adjoining tenants. Where the street is paved the paving shall be kept separate from the other material excavated. (It is generally desirable to place the paving material on the side of the trench which is to be left open for travel, and the earth upon the other.) All streets shall be kept open for travel and the engineer reserves the right to require the use of excavating-machinery if necessary to insure this.

No tunnelling will be allowed except by written permit, with restrictions, from the engineer. When tunnelling, the contractor will excavate the material to such cross-section as may be designated, using timbering or other tunnel-lining and shoring satisfactory to the engineer. The location and size of any shafts, and the location of pumps, derricks, boilers, and other machinery, must be approved by the engineer (see Art. 69). The engineer shall have the right to limit the amount of trench which shall be opened or partly opened at any one time in advance of the completed sewer, and also the amount of trench left unfilled.

The contractor shall not, without permission from the engineer, remove from the line of the work any sand, gravel, or earth excavated therefrom which may be suitable for refilling the trench until the same shall have been refilled.

Paragraph 14. Pumping and Bailing.—The contractor shall furnish all necessary machinery for the work, shall pump, bail, or otherwise remove any water which may be found or shall accumulate in the trenches, and shall perform all work necessary to keep them clear of water while the foundations and the masonry are being constructed or the sewer laid. In no case, unless by special permission of the

engineer, shall water be allowed to run over the invert or foundation or through the sewer until the cement is satisfactorily hardened. The disposal of the water after removal shall be satisfactory to the engineer.

Paragraph 15. Shoring and Sheathing. Whenever necessary the sides of the trench shall be braced and rendered secure and either open or close sheathing used, to the satisfaction of the engineer; such sheathing and bracing to be left in until the trench is refilled, all such bracing and sheathing being done at the contractor's expense. Sheathing left in permanently by the order of the engineer, and only such, will be paid for at the price bid. When left in the trench sheathing shall be cut off at a point about I foot below the surface. The contractor shall, at his own expense, shore up and otherwise protect any building which may, in the opinion of the engineer, be endangered by the work.

Paragraph 16. Railway-crossings.-When any railwaylines are to be crossed or interfered with specific directions as to the time and manner of doing this work will be given by the engineer, and the contractor shall conform to such directions. He shall be allowed for material furnished and made part of the permanent construction, so far as it may be additional to that indicated on the plan, but all other work shall be done at his own cost.

Paragraph 17. Interference with Existing Structures and Watercourses.—In excavating and back-filling trenches and laying the sewer care must be taken not to move or injure any gas-, water-, sewer-, or other pipes, conduits, or structures without the order of the engineer. If necessary the contractor shall, at his own expense, sling, shore up, and secure, and maintain a continuous flow in said structures, and shall repair any damage done to them and keep them in repair until the final acceptance of the completed works, leaving them in as good condition as when uncovered. Should it be necessary

to move the position of a pipe or conduit this shall be done in accordance with the instructions of the engineer, and the contractor shall be allowed for material furnished and made part of the permanent construction, so far as it may be additional to that indicated upon the plans, and for labor performed on such additional construction, but all other work shall be done at his own expense.

At such street-crossings and other points as may be directed by the engineer the trenches shall be bridged in a secure manner, so as to prevent any serious interruption of travel upon the roadway and sidewalks and also to afford necessary access to public and private premises. The material used and mode of constructing such bridges and the approaches thereto must be satisfactory to the engineer; the cost of all such work must be included in the regular price bid for the sewer. (Crossings should not be tunnelled under, since it is almost impossible to so refill the tunnels as to prevent aftersettlement, but should be bridged. Direct access to the street should be given to fire-engine houses and usually to liverystables.) All fire-hydrants shall be left uncovered and accessiThe contractor shall at his own expense provide for all watercourses, gutters, and drains interrupted by the work, and replace them in as good condition as he found them.

ble.

Paragraph 18. Rock Trenches.-When the excavation for a pipe sewer or drain is made through rock or other material too hard to be readily or conveniently removed for admitting the hubs of the pipe the trench shall be excavated at least 4 inches deeper than the grade of the outside bottom of the pipe and [filled with concrete up to and around such pipe, as shown upon the plans] [refilled to such grade with sand or loam, free from stones or other hard substances, thoroughly rammed]. When rock is encountered in the trench it shall be stripped of earth and the engineer notified and given proper time to measure the same before blasting.