1. The testimony admitted at the trial to contradict Bissell was incompetent. It is true that when a witness testifies to a material fact, the party against whom he is called may show, on cross-examination, that the witness has conducted himself as if no such fact existed. Miller v. Stevens, 13 Gray, 282. But we think the evidence had no tendency to contradict him. He had not testified that Hurlburt was insane, or that he thought *200him insane. He was not an expert, and his opinion could not legally be asked or given in evidence, one way or the other. He had testified to certain facts which were offered in evidence on behalf of Hurlburt to show insanity. But it did not follow, from the existence of these facts, that Bissell thought him insane, and the plaintiff had no right to introduce evidence to show that he thought otherwise. It would have been the same if Bissell had been asked directly, “ Did you think him insane ? ” The question would have been inadmissible. The defendants’ exceptions upon this point are therefore sustained.
2. The demurrer was rightfully overruled. The action is rightly brought by Hubbell alone. He alone was interested in the performance of the award by Bissell. His surety was not a party to the submission or the award. The true construction of the agreement is, that Hubbell and Bissell contract with each other, and each has a surety who joins with him in guaranteeing the performance of his part of the contract, but the sureties respectively do not contract with each other.
3. The award including costs, which were not included in the submission, would be rendered invalid ; but as the amount thus awarded is severable, and can be ascertained and distinguished, the action can be maintained upon the part of the award which is good. Caldwell v. Dickinson, 13 Gray, 365.
4. The evidence of the statements of Bissell respecting the award would certainly be competent evidence 'against him, and no ruling was asked in regard to its competency as affecting Hurlburt.
5. The oiler to show “that the award was erroneous, and comprised errors and mistakes,” was too vague and general. It is only some particular kinds of errors and mistakes which will vacate an award. Errors of opinion and judgment will not. Errors of computation may. But a general ruling of the court will not be treated as erroneous, when there is nothing in the exceptions to show that, in relation to the case on trial, it was not perfectly correct. It is for the defendants to show that the evidence offered was competent, if they would sustain their exception to its rejection. In the form in which they offered it, it *201might or might not have been so; that question depending upon circumstances not reported.
6. The statements of one of the arbitrators, made after the award was published, could not be evidence against either party. His functions had ceased, and evidence of what he said was mere hearsay. He must testify to any material fact, like other witnesses.
7. The defendant Hurlburt was allowed to show by paroi that there were matters included in the award not included in the submission, and the jury were instructed that, if proved, this would be a good defence for him. But the court confined him in this proof to matters not appearing upon the award and submission themselves. Upon these the court ruled as a matter of law; and, as we have seen, ruled correctly. The defendants have therefore no cause of complaint on this point.
As it is desirable that this vexatious litigation should end within some reasonable period, and as the only exception sustained concerns the defendant Hurlburt only, and has a bearing upon a single ground of his defence, we do not think it necessary or proper to order a new trial, except upon the condition that it shall be confined to the single issue of Hurlburt’s competency to contract at the time he signed the agreement as surety to Bissell. If Hurlburt elects a new trial upon this point, he is entitled to it; otherwise there must be judgment upon the verdict.