The court erred in ruling that there was no proof of the due execution of the paper offered by the defendant to be submitted to the jury. Although the plaintiff denied that *297there was a seal upon it when he affixed his signature to it and the subscribing witness was unable to testify to the fact, yet the instrument itself, when it was signed by the plaintiff, purported to be under seal. It was therefore on its face a direct and solemn admission in writing by the plaintiff that the instrument was then under seal, and well authorized the defendant to contend before the jury that the plaintiff, in denying that the instrument was under seal when executed by him, was either mistaken or testified falsely. A party is not estopped to affirm s. fact material to the issue, because it has been denied by a witness called by himself. If it were so, he might be compelled to sacrifice his case by putting on the stand an adverse and corrupt witness whom he was obliged to call. A party may (ontradict, but cannot impeach his own witness. Brown v. Bellows, 4 Pick. 194.
But the ruling of the court on this point, although erroneous, was immaterial to the issue on trial, and does not entitle the defendant to a new trial. The instrument offered in evidence constituted no bar to an action on the mortgage. It was neither a release, nor a covenant not to sue the mortgage. It did not even a mount to an agreement by the plaintiff that the mortgage was invalid. He did not agree that he would not foreclose it or enforce it by suit. It was only an agreement that the defendant might use the name of the plaintiff, in case she should find it necessary to do so in order to contest the validity of the mortgage. If the plaintiff has committed a breach of this agreement, the damages thereby sustained would not necessarily be equivalent to the value of the mortgaged estate. Such breach therefore could not be set up and supported as a bar to this suit in order to avoid circuity of action.
Besides, it does not appear that the use of the plaintiff’s name could in any way have availed the defendant in contesting the validity of the mortgage. Every ground of defence was open to her in this action, and the jury have found that the mortgage was valid. It does not appear that the verdict would have been different, if the action had not been in the name of the plaintiff, but had been brought by the original mortgagee or any other person. Exceptions overruled.