The amount sued for was $782.17, of which the sum of $35.92, the aggregate of some small deductions upon other contracts, was disallowed by the court of claims, and that result accepted by the claimant. It appears from the third finding that the postmaster general deducted from the claimant's compensation, under contract No. 46,118, $746.25, 'which deduction equals one-quarter of the total compensation fixed by the contract for whole service under it during the period covered by the alleged delinquency;' being the three years and three quarters from July 1, 1878, to March 31, 1882. It follows, then, that the contractor performed the service for the months of April, May, and June, 1882, as required by the contract, as hereafter considered. As to $398 of the $746.25, that sum was withheld from the compensation under the contract in question, the last two quarters not having been paid, but the balance of $348.25 was deducted from moneys coming to the petitioner on other contracts; and he contends that it should not have been so deducted, because that amount had been voluntarily paid by the United States, and, therefore, could not be recovered back. But, if the contractor was not entitled to $746.25 of the compensation provided by this contract, and if payments were made thereon up to the last two quarters, by mistake, for service that had not been performed, or under such circumstances as brought them within section 4057 of the Revised Statutes, then the payments could be recovered back, and their deduction in part from other money coming to petitioner was proper, in the settlement of the accounts between the parties. Section 4057 is as follows: 'In all cases where money has been paid out of the funds of the post-office department under the pretense that service has been performed therefor, when, in fact, such service has not been performed, or as additional allowance for increased service actually rendered, when the additional allowance exceeds the sum which, according to law, might rightfully have been allowed therefor, and in all other cases where money of the department has been paid to any person in consequence of fraudulent representations, or by the mistake, collusion, or misconduct of any officer or other employe in the postal service, the postmaster general shall cause suit to be brought to recover such wrong or fraudulent payment or excess, with interest thereon.' This section was applied in U. S. v. Barlow, 132 U. S. 271, 281, ante, 77, and Mr. Justice FIELD, in delivering the opinion, quotes with approval the language of Baron PARKE in Kelly v. Solari, 9 Mees. & W. 54, 58, that 'where money is paid to another under the influence of a mistake, that is, upon the supposition that a specific fact is true which would entitle the other to the money, but which fact is untrue, and the money would not have been paid if it had been known to the payer that the fact was untrue, an action will lie to recover it back, and it is against conscience to retain it,' and adds: 'Reasons for the application of the rule are much more potent in the case of contracts of the government than of contracts of individuals; for the government must necessarily rely upon the acts of agents whose ignorance, carelessness, or unfaithfulness would otherwise often bind it, to the serious injury of its operations.' Nothing more need be said on this point, and this brings us to the real question in the case.

Claimant contracted to carry the mails 'from Salinas, by Santa Rita and Natividad, to Gabilan, 15 miles, and back.' The time to be taken on the trip was specified at six hours each way. There is no ambiguity in this contract, from which a doubt could arise as to whether the return route was to be identical with the outward route. Where places are designated as on the line of a mail route from one point to another and back, no reason is perceived for their omission on the return. There may be instances where retracing the road is not deemed important, or is impracticable, in view of particular exigencies; but, if so, the difference in route would be specified. And, where the transportation is for a given number of miles and back, this does not mean the number named one way and an indefinite and less number the other. The contractor was clearly required to return to Salinas from Gabilan by the same way he went to Gabilan from Salinas. The court of claims did not take any other view of the language of the contract, but determined the case to the contrary, upon the ground that the contract had been otherwise 'construed by the claimant, and the responsible power of the defendants, and that construction became and was the contract at the time the services were performed, covered by the period of deductions.' This conclusion is reached as to the post-office department upon the reasoning that, as 'it was the duty of the postmasters connected with the mail route at the termini to report to the department the manner in which the service was performed, and the presumption is that they performed their duty, and that the department was advised, not only during the time of the performance of the contract in controversy, but the antecedent contracts, covering the same service embraced in contract No. 46,118,' and as the evidence was 'that on October 23, 1878, the acting second assistant postmaster general certified to the auditor of the treasury for the post-office department that for the quarter ending September 30, 1878, there had been no failure or delinquency in the execution of the contract upon the part of the contractor,' and as 'it is safe to assume that for all preceding payments the same certificate was made, based upon reports furnished by the postmasters connected with route No. 46,118,' the acts of 'the responsible officers of the department, being in possession of the same information and knowledge' as the postmasters, 'commit the defendant to the construction of the agreement as placed upon it by the parties who performed the labor of its execution, and who were cognizant of the mode in which it was performed.' The department did not direct, or affirmatively permit, the contractor to pursue the course he did; and, if he could recover in whole or in part upon the ground of an acquiescence equivalent to assent in a certain mode of dealing with the subject-matter of the contract, the burden was on him to show knowledge or information by the department of his conduct in the premises. No evidence to establish such knowledge or information having been adduced, the case was made to rest upon the presumption that the postmasters at the termini where the schedules of the time of the arrival and departure of the mails were kept, an registers thereof made and returned, were acquainted with the terms of the contract, and claimant's non-compliance therewith, and this being presumed upon the further presumption that they must have reported the failure in performance to the department. In U. S. v. Ross. 92 U. S. 281, 284, Mr. Justice STRONG, speaking for the court, says: 'The presumption that public officers have done their duty, like the presumption of innocence, is undoubtedly a legal presumption; but it does not supply proof of a substantive fact. Best, in his Treatise on Evidence, (section 300,) says: 'The true principle intended to be asserted by the rule seems to be that there is a general disposition in courts of justice to uphold judicial and other acts, rather than to render them inoperative; and, with this view, where there is general evidence of acts having been legally and regularly done, to dispense with proof of circumstances, strictly speaking, essential to the validity of those acts, and by which they were probably accompanied in most instances, although in others the assumption may rest on grounds of public policy.' Nowhere is the presumption held to be a substitute for proof of an independent and material fact.' Section 3849 of the Revised Statutes provides that 'every postmaster shall promptly report to the postmaster general every delinquency, neglect, or malpractice of the contractors, their agents or carriers, which comes to his knowledge.' By none of the findings of fact is it shown that the delinquency in question ever came to the knowledge of the postmasters at the termini of this mail route; but under finding 6 it appears that 'on March 22, 1882, second assistant postmaster general addressed a letter to the postmaster at Natividad, and received information from him on April 6, 1882, that the mail was not carried from Gabilan by way of Natividad and Santa Rita, and that such had been the practice since the present contractor had the contract. The postmaster at Santa Rita certified to the postmaster general that such had been the practice since he became postmaster. The date of the letters as to the continuance of the mode of carring the mails was May 1, 1882;' and, from finding 3, that the postmaster general instantly repudiated that manner of carrying the mails, and that they were not so carried for the remaining quarter, under the contract. Of course, the postmasters at Santa Rita and Natividad knew that the mails did not come back through those places, but it does not follow that they were aware that the contractor was obliged so to carry them. Indeed, as they made no effort to have this state of things remedied, so far as appears, it is rather to be presumed that they were not aware that it was the result of the delinquency of the contractor. The fact of knowledge on the part of the postmasters of the delinquency, from which the inference is drawn that they reported it, was a fact to be proven, and not to be presumed. If they knew of the delinquency, it was undoubtedly their duty to report it, but it is not to be assumed that they did report it, without some evidence of such knowledge; and, upon this record, the irresistible inference is that the delinquency, if reported, would not have been permitted to continue. The certificate of the second assistant postmaster general is dated October 23, 1878, and states that the mails had been carried 'without any failures or delinquencies, so far as shown by returns received, for the quarter ended September 30, 1878.' As the contract was a plain one, and was not performed according to its terms, we think this certificate indicates clearly that the 'returns received' did not show the non-performance. So far from strengthening the alleged presumption that the postmasters reported the facts as they existed, its effect is to the contrary. What they did report, in fact, is not shown; and, inasmuch as under finding 6 no other inference can be drawn than that the first information that the postmaster general had that the mail was not carried f om Gabilan by way of Natividad and Santa Rita was April 6, 1882, we cannot accept the conclusion that the responsible officers of the department were in possession of information and knowledge of the conduct of the contractor before that time, and acquiesced in the manner in which he carried the mails during the period in question or during the preceding years, in respect to which it is found that he so operated the route under a similar contract. We can find nothing in the findings to justify us in holding that the department paid this claimant the full measure of his compensation prior to March 31, 1882, with knowledge of the manner in which he was performing the work, or that the department ever put the interpretation upon the contract which is now contended for, or induced the contractor to enter into the contract by reason of any such interpretation on its part. The deduction of $746.25 was properly made, and the conclusion of law on the facts found was erroneous. The judgment is reversed, and the cause remanded, with directions to enter judgment for the United States.