(b) A suspicion of favoritism or of collusion is difficult to live down.

(c) It is possible that other manufacturers may be able to furnish a better article. Word the specifications so as not to deprive the Contractor of some option in the matter.

65. Impossibilities. Do not attempt the requiring of impossibilities.

It is essential that the Engineer appreciate the limitations of the material he expects to use. Not less necessary to him is an intimate appreciation of the average skill and habits of work of the men employed in the various building trades, for it is practically impossible to secure even from skilled mechanics a grade of workmanship much superior to that to which they have been long accustomed.

66. Grades of Quality. It is perhaps unnecessary to remind the student of the futility of calling for or expecting to get "perfect" materials or workmanship of any description. It is not in all cases even necessary that these should be of the best quality (unless absolutely nothing else will serve). The Engineer should study his available materials and aim to make his specifications explicit respecting the grades of each he requires. Stone masonry, for example, costs anywhere from five dollars to fifty dollars or more a cubic yard, depending partly on the stone and the labor of quarrying and laying it, but much more on the amount of labor spent in dressing the surface to various finishes. Timber and lumber can generally be furnished in at least two grades, the best of which has certain well recognized imperfections. Second-hand steel rails or second-grade pipe will for some purposes be as serviceable as the newest and best

and so on through a long list. The classic definition of a Engineer describes him as a man who can do for a dollar what any ignoramus can do for two.

67. Results Versus Methods. Specify results rather than methods. Aim to describe the finished structure with its constituent materials. There are two objections to specifying methods:

(a) It is possible that methods preferred by the Contractor may be more efficient.

(b) It will be impossible in such case to hold the Contractor to definite results.

Under some circumstances the Owner or the Engineer may be perfectly willing to accept results, in which case it is entirely reasonable to restrict the Contractor to a well-defined method.* Or it may be advisable to prescribe a method in detail, following the prescription with a statement that the Contractor will be allowed, by express permission of the Engineer, to substitute a method which he (the Contractor) is willing to guarantee will produce an equally good result. Cases of bridge erection have been dealt with thus.

Not many years ago all concrete was hand mixed, and specifications prescribed the process in great detail. Most types of machine mixers do the work at least as well, so that few specifications now define the method of mixing.

68. Balanced Treatment. Important and essential features of the design should have the fullest and most explicit treatMatters involving much labor or expense need to be explained in greatest detail, whereas some points involving no additional expense can often be passed over with few words or even in silence.

The student may criticize and rewrite the following:

(i) (From specifications for masonry wall.) "The stone must be of limestone, sandstone or granite, of quality, size and shape acceptable to the Engineer."

(ii) (From specifications for a tunnel.) "Concrete lining shall be placed throughout the tunnel as indicated by the drawings. Any excavation beyond the neat lines of the tunnel section as shown on the drawings shall be filled to the satisfaction of the Engineer and no allowance will be made therefor."

(iii) (From specifications for concrete culvert.) "Concrete shall be composed of one part cement, two parts sand and four parts crushed stone."

(iv) (From specifications for a dam.) "In this excavation the kind of explosives used, the amount of the charges, the depth and direction of the holes, and the entire process of the work shall be under the direction of the

* A case in point is the stipulation that structural steel shall be manufactured by the open-hearth process.

Engineer, the object being to do the work in such a manner as to avoid fissures in the remaining rock. If at any place the Contractor shall excavate, damage or shatter the bed rock beyond the lines given by the Engineer to be excavated, and it is necessary to replace the solid rock by masonry, then the Contractor shall supply such masonry free of cost to the Owner."

CHAPTER XIII

OUTLINES OF SPECIFIC CLAUSES

The following outlines are designed to furnish the student practical drill in the writing of the specific clauses of specifications for work of a comparatively simple nature. The student should consult the references in the Appendix, as well as any actual specifications which may be available, before proceeding with the composition. He should aim, however, toward a moderate degree of individuality of expression from the first, and his efforts in this direction should be subjected to the criticism of the Instructor, and possibly of the class.

Standard Specifications. For some years past there has been a movement toward standardizing the specific clauses of specifications for certain classes of work, or for certain materials. For example, each of the more important railway systems has prepared for its own use a set of "general" or "standard" specifications for masonry construction, a set for track laying, etc. Various individual engineers, or associations of engineers or of manufacturers have evolved "general" or "standard" specifications for steel construction, for pavements, for cement, for timber, etc. The student will find a number of these noted in the references in the Appendix. He would do well to secure some of them for his personal library.

69. Vitrified Pipe Sewer.

(a) Preparing Trench.

(i) In earth: -dimensions of trench; limit of length left open ahead; tunnelling; treatment of unstable subsoil.

(ii) In rock:- rock classification; section paid for;* excavated ( ) feet in advance.

* In sewers and similar work involving rock excavation, the student should realize that it is unnecessary and practically impossible to excavate rock, unless it be soft, to a line. Hence arises the necessity in most instances of fixing in the specifications (sometimes on the plan) a limiting section, beyond which, if the Contractor excavates, he cannot expect compensation. In trench excavation this limiting section has been variously fixed as a rectangle, a trapezoid, or a combination of the two.

(iii) Miscellaneous contingencies: - intersecting drains, etc.; pumping; shoring or bracing; protection of existing structures (pipes, conduits, railway tracks, etc.).

(b) Mortar and Concrete.

(i) Requirements for cement (soundness, fineness, strength, etc.).

(ii) Quality of sand..

(iii) Size and quality of stone.

(iv) Proportions for mortar and concrete.

(v) Mixing; laying; protecting; binding.

(c) Pipe.

(i) Measurement of total length.

(ii) Quality and dimensions of pipe and specials. (iii) Preparing bed.

(iv) Laying; jointing; cleaning, etc.

(v) House connections (or Y branches); size; frequency; capping; marking.

(d) Accessories.

(i) Manholes:

steps; head; cover.

(ii) Flush tanks.

(e) Backfill.

quality of material; method of erection;

(i) Near pipe and elsewhere.

(ii) Tamping or puddling.

(iii) Replacing pavement (or covering pipe if laid on

surface).

(iv) Limit left uncovered.

(v) Deficiency supplied.

(vi) Disposal of surplus.

(vii) Overhaul.

(viii) Cleaning up.

70. Macadam Road.

(a) Grading.

(i) Excavation: - classification and measurement; treatment of spongy material; disposal of surplus.