The plaintiff agreed with the defendant, by written contract, to fill with gravel a certain district described in an order of the superior court for the transaction of criminal business, which was issued for the abatement of a nuisance caused by stagnant water. By the terms of the contract, and as a mode of fixing compensation, the amount of gravel deposited in filling it to a fixed grade was to be measured on the ground by the city engineer, whose measurements were to be conclusive. After the work was done, the defendant received two certificates or returns of the city engineer, stating the amount, the last of which purported to be a revision and correction of the first.
*387It appeared at the trial, that the certificate of the engineer waa made from notes of his assistant, to whom he gave directions beforehand, and from his own subsequent examinations and verifications of the levels; that he was there from time to time, but his assistant made no measurements in his presence, and none were made by him in person; and that this work was done by his assistant, as he did such work generally. The defendant himself testified, that he was informed, before the work was begun, that the assistant would superintend it for the engineer, make the surveys and fix the grades ; and that he afterwards pointed out to him the lot to be filled, gave directions about staking it out, and other directions about it, and was there while the work was going on, and had been there to see it frequently. It is apparent also, from the certificate of the engineer, that the nature of the filling was such as to require some allowance for the settling of the original surface while the filling was going on ; and that an estimate of quantity, beyond the results attainable by mere measurements and mathematical computation, would be required, in justice to the contractor.
It was objected by the defendant, that the certificate of the engineer could not be conclusive, because the measurements were not made by him in person or in his presence.
The validity of this objection depends upon the fair interpretation of this provision in the contract. The written instrument is indeed the sole repository of the agreement of the parties. Its construction is matter of law for the court. If its terms are used in no peculiar or technical sense, or as applicable to a particular kind of business, they must have the meaning usually attached to the words used. But a true interpretation requires that they should be applied to the subject matter, the situation of the parties, and the usual and known course of business. The common meaning of words and expressions, otherwise clear and unambiguous, may thus be modified by paroi, without invasion of the rule which makes the writing the proper and only evidence of the agreement. Thus it was recently held that the word “ published,” in a written contract relating to advertising charts, had no fixed signification which the court could apply to the contract, *388and what was a sufficient publication must be determined by the jury in view of all the facts; Stoops v. Smith, 100 Mass. 63 that “ horn chains ” might mean chains made partly of horn and partly of hoof ; Swett v. Shumway, 102 Mass. 365 ; and that the words 11 each room,” used in an application for insurance, might mean each whole story in a mill, although there might be more than one room in each story; Daniels v. Hudson River Insurance Co. 12 Cush. 416, 429. In Herrick v. Belknap, 27 Verm. 673, it was held that a stipulation, in a contract for the construction of a railroad in part, “ that the engineer shall be the sole judge of the quality and quantity of the work, and from his decision there shall be no appeal,” is binding upon the parties, and constitutes the engineer an arbitrator or umpire between them, and that such stipulation, construed with reference to its subject matter, does not require the estimates to be made by the chief engineer, but has reference as well to the assistant or resident engineer.
The reference in the contract here under consideration is to the city engineer, an officer who is charged with certain defined duties, in the performance of which he usually depends upon the assistance of others. He is referred to, not by name, but by his official title. It is very properly conceded, in the argument of the defendant, that the work required the employment by him of servants and agents; and the question is, how far the work must have been under his direct personal supervision. The measurements are to be made indeed upon the ground, as contra-distinguished from measurements in the pit, or in the carts. But it is too narrow an interpretation to insist that they shall be made by the engineer in person, or in his actual presence. If made in the usual manner, by his assistants, according to his directions ; if subsequently revised by him, so far as the nature of the work would admit, and made the basis of an estimate of quantity depending not wholly on computation ; and if then certified by him to be correct; the jury may properly find that there has been a substantial performance by the city engineer of the duty which by the fair construction of the contract the parties intended. The instructions and rulings of the court upon this point of the case are not open to exception.
*389It is farther strenuously objected, that the rule laid down at the trial as to the weight to be given to the measurements and estimates of the engineer was erroneous. By the agreement, he is made the sole and final judge in a matter where it was evidently considered difficult to attain entire accuracy. This agreement, made by competent parties upon a good consideration, it is the duty of the court to enforce. A reference to a third person to fix by his judgment the price, quantity or quality of material, to make an appraisement of property and the like, especially when such reference is one of the stipulations of a contract founded on other and good considerations, differs in many respects from an ordinary submission to arbitration. It is not revocable. The decision may be made without notice to or hearing of the parties, unless such notice and hearing be required by express provision or reasonable implication; and it may be made upon such principles as the person agreed on may see fit honestly to adopt, or upon such evidence as he may choose to receive. Without doubt he may, within reasonable limits as to time, revise and alter his decision, when it can be done without prejudice to the rights of either party. In one important respect it is to be treated precisely like an award under a submission to arbitration. It cannot be impeached for mistake arising from error in the judgment of the referee, or in drawing conclusions from evidence and observation. To avoid it, the mistake must be one which shows that he was misled, and so far misapprehended the case that he failed to exercise his judgment upon it; as where he is imposed upon by false measures or false weights, or there is obvious error in figures. Vanderwerker v. Vermont Central Railroad Co. 27 Verm. 125, 137. Boston Water Power Co. v. Gray, 6 Met. 131, 169. Fraud practised upon him, or by him, will of course defeat it. Smith v. Boston, Concord & Montreal Railroad Co. 36 N. H. 458, 490. Mickles v. Thayer, 14 Allen, 114.
The instructions upon this point, as we understand them, and as they must have been understood by the jury, in their application to the facts presented in evidence, and to the points made at the trial, were consistent with the rules and distinctions here stated. It is true, the jury were told that the return of the en*390gineer, if neither he nor his assistant was guilty of fraud, could not be set aside for mistakes; but we cannot see, from the report, that this was not sufficiently accurate to meet the exigencies of the case. It would seem that the alleged mistake was wholly in the over-estimate of the work by the engineer, and was an error of judgment only. The case did not turn upon the distinctions indicated.
The principal objection remaining to be considered arises also, as we think, from an erroneous interpretation of the ruling. It is urgently insisted, that, while either party might waive a literal compliance with the terms of the contract, neither party could alone waive the performance of his duty by the engineer, so as to substitute in his place another person, whose measurements should be conclusive. And this is true. But the correctness of the ruling, as applied to the facts here, and as connected with the other instructions, is not affected by the proposition. The whole case proceeded upon the theory that it was the estimate of the city engineer which was or was not conclusive. The evidence did not show an attempt on the part of the defendant to substitute any one in his place. On the contrary, the defendant accepted and acted upon his report. No particular instructions were asked upon the distinction now taken; and the jury in fact found, under the instructions which were given, that the engineer substantially performed the duty assumed. It is plain that the waiver, contemplated in the ruling complained of, was not a waiver of the substantial performance of the duty imposed on the engineer, and the substitution of another in his place, but a waiver which had reference to the details of the mode in which he reached the result through the assistance of another. Thus construed, we cannot see that it injured the defendant. The defendant is to be treated as the real and only party in interest; his acts and admissions, whether by express declarations or implied from conduct, are to have full effect in favor of the plaintiff; and it makes no difference that he was acting under the order of the court, in his official capacity, and has the right to look to others for indemnity.
Upon the whole, we cannot see in the instructions and rulings given, or in those refused, any reason for disturbing this verdict.
*391The conversation between Crafts and the witness Moses was properly excluded. The plaintiff put no part of it in, and Crafts had not then been examined. Judgment on the verdict.