By the Court.
Starnes, J.delivering the opinion.
[1.] The question first to be considered, relates to the admission, in evidence, of the oral understanding stated by the witness, Robert B. Lester, to have been made with him as agent for the defendant in error.
The principle is plain and familiar, that all oral negotiations, conversations and agreements between the parties to a written contract, in relation to the subject matter thereof, which precede or accompany the instrument, must be treated as merged in it; and the latter is to be received as the sole evidence of what was agreed upon or contracted by the parties.
It is our opinion, however, that this principle did not operate to exclude the oral agreement testified to by Lester, notwithstanding the subsequent execution of the instrument which was in evidence. The date of that instrument was the 2d day of January, 1852, and the witness proves that sometime in August or September following, the plaintiff in error informed witness, that the grading on the Muscogee Rail-road was finished, and asked his consent, as agent for the defendant in error, that he should be allowed to take the slave Tom to Brunswick ; which request was refused. He also swears, that the plaintiff in error then said, that he would put Tom to repairing the track of the South-western Rail-road, and that in a few days thereafter, he came to the witness and told him that he had not sent'the slave to work on the said road; but that he had gone off with the overseer and hands to Brunswick. In another place, the witness represents the plaintiff in error, as saying, that the overseer had carried Tom with him, without his consent.
*414If we analyze this evidence, we will find it showing these things : 1. That the plaintiff in error had asked the consent of the witness, as agent of the defendant in error, to the removal of Tom from the Muscogee Rail-road to Brunswick. And it seems fair to infer that he would not have asked such consent, if there had been a general contract of hiring between them, and not a contract restricting the employment of the slave, in whole or in part, to this Road. 2. That the plaintiff in error quietly acquiesced, when such consent was refused, and said he would put Tom to work on the track of the South W. Rail-road, by which, the conclusion is authorized, that the slave was not hired generally, but with reference to employment, at least in part, on the Road last mentioned. 3. That in a few days after, the plaintiff in error went to the witness, and announced that Tom had gone off with the overseer and hands to Brunswick, and .said that the overseer had carried him off without his consent. Which latter fact seems to justify the inference, that there was something wrong in this removal of the slave, or the plaintiff in error would not thus have sought the witness and apologized for it, as it were; and indeed, that if he had hired the slave in a way which would have given him the right to remove him to Brunswick, he would not have withheld his consent that the overseer should remove him.
These things, all taken together, afford presumptive evidence, so strong as not to be resisted, that the parties had, at some time previous to August or September, 1852, entered into an agreement, to the effect, that the slave Tom was not to be employed by the plaintiff in ei’ror, wheresoever he might choose to to take him; but that he was hired to work on the two Rail-roads specified. Such restricted agreement, however, was not in the written instrument; and by legal intendment, it could not have been made before, or at the time of the execution of that instrument, because it would have been extinguished by the latter. It must, then, have been entered into subsequently.
Regarding such subsequent contract, as being thus presumptively shown to have been orally made, this testimony of the verbal negotiations, previous to the date of the writing, was *415proper for the Jury, as serving to throw light upon the nature and character of the subsequent, understanding: and the same were in aid of the strong presumptive evidence which has been just detailed. Not as proving that such oral agreement was made and entered into, before or at the time of the execution of the instrument, but as serving, by a detail of preliminary negotiations, to show, more clearly, what must have been the subsequent agreement otherwise proven to have been made.
Whatever, therefore, may have been the reasons of the Court below, for the admission of this testimony, in this point of view,, it went properly to the Jury.
[2.] The next.and only other question presented for our consideration, by the Counsel for the plaintiff in error, was the competency of this witness to prove that he entered into the contract, as agent for the defendant in error.
Nothing is better settled, than that the cases of agents, carriers, factors, brokers, and other servants of this description, in consideration of public convenience and necessity of trade and commerce, and to prevent a failure of justice, constitute a class of special exceptions to the general rule, that a witness, interested in the subject of the suit, or in the record, is not competent to testify on the side of his interest. (Bull. N. P. 289. Matthews vs. Heydon, 2 Esp. 509; Poth. on Obl. by Evans, App. No. 16, p. 208, 267. 1 Phil. Ev. 140. 1 Stark. Ev. 113. 1 Greenlf. Sec. 416.)
And this extends, in principle, to every species of agency or intervention by which business is transacted, unless the case is; overborne by some other rule. (1 Greenlf. Ev. See. 416.)
Judgment affirmed. ■