Lowe, O, J.
I. Under the issue, as it was made up, the interpleading claimants had the affirmative, and therefore there was no error in ordering that they should open and close the argument to the jury.
II. J. B. Field testified to the indebtedness of the firm of Green, Thomas & Co., to claimants, as the consideration of the assignment of the judgment to them, and in doing so referred to certain letters which had passed between the claimants and Ed. II. Thomas, as the source in part of his information on this point. The plaintiff moved the court to exclude the testimony unless the letters were produced, which the court refusing to do is now urged as error. The answer to this point is that the knowledge of the witness was derived only in part from the letters in question, and to enable us to determine intelligently whether his entire evidence should be excluded for such cause, a more specific and panticular statement should have been elicited from the witness, as to the sources of his information. "Wherever an error is complained of it should be made to appear not only affirmatively but with reasonable certainty. In addition to this it is worthy of remark that the same fact was abundantly established by two other witnesses, Thomas and Warren.
III. But as they were defendants in the execution and garnishment, the admissibility of their testimony is assigned as the third error. This relation to the parties however does not affect their competency upon the score of interest, as before held by this court in 7 Iowa 475, and 4 Ib. 44.
*518IY. The next principal error insisted upon was the refusal give to the jury the following instruction asked by the plaintiff: “ That E. H. Thomas, being one of the original debtors, could not at the same time be the agent of the assignees and could not act in both capacities of assignor and agent of assignees; and the assignment would be invalid and of no effect until theassignees’ assent was obtained, and until they had notice of such assignment.” The evidence to which this instruction relates, and upon which it is founded, was that Ed. II. Thomas, who was one of the plaintiffs in the judgment against Armstrong, and one of the defendants in the judgment which the plaintiff held against Green, Thomas & Co.; was also the authorized agent of the claimants ; that he assigned the judgment against Armstrong to the claimants, on the 12th of November, 1858, and communicated that fact on the following day to the assignees by mail, which would not reach them short of four or five days ; ■that on the same day that the notice of the assignment was forwarded to the assignees at Portland, in the State of Maine, the garnishee notice was served upon Armstrong.
. Now the forgoing instructions required the court to lay down two propositions of law to the jury.
First: That while Ed. H. Thomas as a member of the ■firm of Green, Thomas & Co., could assign the judgment which they held against Armstrong, to the claimant, he could not as their agent accept such assignment so as to make it complete in law at the date of the transfer.
Second: That an assignment of this description was not effectual in law until notice to, and acceptance by, the assignees, so as to defeat an intervening garnishment.
With regard to the first question, we readily understand the réason why an agent cannot act so as to bind his principal when he himself has an adverse interest. The nature bf the engagement requires the exercise of disinterested skill and diligence on the part of the agent. For this reason he is not allowed to buy for another goods belonging to *519bimself, nor can he become the purchaser at a sale made for his principal. If he did either, and thus abused the confidence reposed in him, the injured party would not be bound by the act. But certainly it is not in this sense that the interest of Ed. IT. Thomas, was adverse to, or incompatible with that of his principals in Portland, when as their agent, he accepted the assignment in question. If the assignment was legal, and for a valuable consideration, the judgment passed out of the control of Green, Thomas & Co., as a firm, and as such we can perceive no sound reason why Thomas, as the agent of the claimants, might not only aeeept the assignment, but have taken the management of the collection of the judgment and paid the proceeds over, when collected, to his principals ; and this very point was adjudged to be proper in the case of Tompkins v. Wheeler, 16 Pet. 220, where the assignor, agent of the assignee, continued in possession of the unsettled accounts and choses in action which had been assigned, and collected the same for the benefit of the assignee. This same authority held, as it had been before held in the same court in the case of Marlury v. Brooks, 11 Wheat. 96, that an assignment for the benefit of creditors is valid, although their assent is not given at the time it was made. The object being beneficial to the creditor, his assent may be safely presumed. Such certainly is the doctrine as applicable to general assignments made to trustees for the benefit of creditors. And we are inclined to think, that out of New England, the weight of authority is that the assent of absent persons to special assignments, will be presumed unless this dissent be expressed, if made, as in this case, for a valuable consideration and beneficial purpose. 2 Kent Com. 704, 1 Am. L. C. 96. A letter assigning personal property to an absent creditor for the indemnity of himself, or of himself and others, and sent by mail, takes effect from its date. Dargon v. Richardson, 1 Lou. 197, 218.
As now advised, we cannot say that the court erred in refusing to give this instruction. In regard to the other questions *520raised, they are not of a character demanding a distinct notice, and the judgment below must be affirmed.