
84 U.S. 384 (1873)
17 Wall. 384
STITT
v.
HUIDEKOPERS.
Supreme Court of United States.

*393 Mr. G.W. Guthrie, with whom were Mr. J.K. Kerr and Mr. E.S. Golden, for the plaintiff in error; Mr. W.D. Davidge, contra.
Mr. Justice MILLER delivered the opinion of the court.
The argument, as is generally the case when such a transcript as the one in this case comes before us, has been largely made up of controversies as to what the evidence establishes, which was proper for the consideration of the jury but is out of place in a court of errors.
It will not be profitable or necessary to notice all the alleged errors in this decision. Those alone which are decisive of the case will be considered. The remainder may be treated as not well taken or not presented by the record.
One of the errors assigned and insisted on grows out of the conflict in the testimony between the plaintiff and the two defendants, all of whom were sworn as to two papers, which the defendants aver were signed by them and delivered to the plaintiff at the time the escrow was signed, one of which limited the time within which the plaintiff could pay the money and take up the deed to the 1st of December, *394 and the other agreed to give him $2500 out of the $40,000 so paid. No such papers were produced, and on this point the testimony is conflicting. The plaintiff denies the receipt of any such papers, and both the defendants swear positively to their delivery to plaintiff.
On this subject the court charged the jury "that it is a rule of presumptions that ordinarily a witness who testifies to an affirmative is to be preferred to one who testifies to a negative, because he who testifies to a negative may have forgotten. It is possible to forget a thing that did happen. It is not possible to remember a thing that never existed."
We are of opinion that the charge was a sound exposition of a recognized rule of evidence of frequent application, and that the reason of the rule, as stated in the charge, dispenses with the need of further comment on it here.
Leaving to the jury the question of the existence of this limitation of the contract, the court charged in various shapes that, if there was such a limitation, after its expiration, or, if there was none, then, at any time before the payment of the money, the defendants had a right to withdraw the escrow and terminate the plaintiff's agency without accountability to him.
And this view put forth by the court, which was the turning-point in the case, is the error much insisted on here, and assigned in various forms.
The proposition may be looked upon in two aspects: 1. As regards a sale to plaintiff himself, on his payment of the $40,000. 2. As a contrivance to facilitate his sale of the lands as agent of defendants. In reference to the first, we are of opinion that as no pretence is set up of any payment or offer to pay until some time in January, 1865, long after the time limited, if there was a limitation, the utmost that can be justly claimed against defendants is, that it was an open offer of sale at a given price, which bound them only on its acceptance and compliance with its terms; and that until that was done the offer was within their control, and it was entirely within their power to withdraw it. It would *395 seem useless to argue such a proposition. But we will mention two considerations which are conclusive:
1. On any other hypothesis, there is a want of consideration in the contract, the defendants being bound for an indefinite period of time to accept the money whenever it might suit the plaintiff to pay it, while he was not bound to pay or abandon the right to pay at any period within any fixed time. 2. That unless the party making such offer could withdraw or terminate it at his pleasure, there would be no means of relieving him from the danger of its acceptance at any length of time after it was made, and under any changes of circumstances which accompanied his offer. And so are the authorities.
If we examine the proposition as one of agency, it is still clearer that unless there was a contract binding the defendants to accept and ratify a sale by the plaintiff for the sum of $40,000 or more, made at any time, they could, before such sale was completed, withdraw and revoke the plaintiff's agency without liability to him on account of the special offer set up by him.
The charges of the court as to the law of this branch of the case, were, therefore, correct.
It is, however, strenuously contended by counsel for the plaintiff, that before the defendants revoked the agent's authority, by ordering Drake Brothers not to deliver the escrow to him, he had made a valid sale within the terms of the offer, which was an acceptance of that offer, and binding on the defendants.
As regards this branch of the case, it is to be remarked that this is not a suit by the supposed purchasers, Backus & Morse, either to enforce specifically that contract of purchase, or to recover damages for its breach. But it is a suit by the agent who negotiated it to recover against the owners of the land what he would have been entitled to if the contract had been carried out. In this view, it is important to remember that if the plaintiff had paid into the hands of Drake Brothers the $40,000 at the time he deposited with *396 them his written agreement with Backus & Morse, he would have been entitled to a delivery of the escrow, and would probably have received it, and thus prevented all controversy.
As he did not do this, it becomes necessary to inquire what he did that could bind the defendants. The written agreement between Stitt on the one part, and Backus & Morse on the other, is in the record. It is an agreement, in effect, that if Backus & Morse shall elect to buy all or any part of the several tracts of land included in the conveyance in escrow to Stitt, within four days, they may do so at the price of $55 per acre, on depositing with Drake Brothers the sum of $10,000; the remainder to be paid within sixty days after the first deposit. On the last of these four days, it appears by an indorsement made by Drake Brothers on this contract, that Backus & Morse paid in the $10,000 and elected to take the whole of the lands; the $10,000 to be returned if the title was not found to be good, and forfeited to Stitt if the balance of the purchase-money was not paid within the time stipulated.
By the agreement as originally made and signed by Stitt, Backus, and Morse, the latter are bound to nothing. They had an option for four days of all or any part of the land at $55 per acre, and they had sixty days after their election was made to pay the principal part of the purchase-money. By their payment of the $10,000, they placed themselves in relation to Stitt in a position where they could forfeit the $10,000 and thereby release themselves, or pay the balance within sixty days and claim a conveyance of the land. Looking to these papers as the proper evidence of the contract between Stitt, on the one part, and Backus & Morse on the other, it is clear that there was never any obligation on the part of the latter to take the land and pay for it at a definite price; that by forfeiting the $10,000 they could be released from any further performance of that agreement.
This statement of the nature of that contract is sufficient to show that it was no compliance with the outstanding offer of the defendants to Stitt.
*397 They had never offered to accept any such contingent or optional contract of purchase, nor had they agreed to accept of any contract on time. Forty thousand dollars paid into Drake & Brother's hands was the only valid acceptance of their offer which could bind them.
The plaintiff offered to introduce some parol testimony to show that the obligation of Backus & Morse was to take and pay for the land as soon as the title could be examined. This was excluded by the court, and its exclusion is assigned for error. While it is certainly true that in some classes of cases a contract between persons not parties to the suit may, when introduced, be contradicted or varied by parol testimony, the principle can have no application in a case like the present. This was a contract concerning real estate, which the statute required to be in writing to make it valid. And certainly the defendants were not bound to accept such an incomplete contract as binding on them, while its obligatory force as to the other party depended on parol evidence.
We are of opinion that no such contract of sale by Stitt was proved as the defendants were bound to accept before they revoked his agency.
An attempt was made to show that the contract with Backus & Morse was ratified by the defendants, and an abstract of title furnished by them was relied on for this purpose. On motion of the plaintiff's counsel the defendants produced what they claimed to be the original of this abstract. The plaintiff thereupon offered a copy of the abstract, which he insisted was different from the one produced by the defendants and which he wished to introduce. This was overruled. It is a little difficult to understand precisely how all this was done, as the bill of exceptions states that the defendants were ready to verify by their oath the genuineness of the abstract which they produced. At all events it seems to us that the court was right in refusing to admit in the first instance what was conceded to be a copy, when that which was *398 at least primâ facie the original was in court to answer the notice of the party desiring to use the copy. How far the plaintiff could have been permitted to show a variance of the defendants' paper from the genuine, after it was once introduced, we need not inquire. But a copy could not be introduced until what seemed to be the original had been before the court and become the subject of inspection by the jury.
It has been urged that the court invaded the province of the jury by giving instructions which left them no alternative but to find for the defendants. It may be true that, under the charge of the court, they could do nothing else. But a careful examination of the whole charge, which is before us, shows that the court left the credibility of the witnesses, and all disputed facts, to the jury, and based its instructions to find for the defendants on their belief of propositions which required such a verdict. This objection is largely based upon the argument that the jury might have found for the plaintiff a reasonable compensation for his services on the common count, but to this it is a sufficient answer to say that no testimony was offered of the value of the services rendered under this count, nor any instructions asked of the court on that count, and that through the whole trial plaintiff insisted on his special contract, and that alone, as the ground of his recovery.
We see no error in the record, and the judgment of the Circuit Court is
AFFIRMED.
