The plaintiff, in April 1861, agreed to serve the defendants for three years, for a stipulated salary, in the capacity of buyer and salesman, and to take the management of their woollen department, and devote his time and attention to their service, according to his best knowledge and ability. They discharged him from their service in the following August. In their answer they deny that he devoted his time and attention to their service according to his agreement. A jury has found that he did, and has returned a verdict for the amount of his claim. The defendants excepted to the exclusion of certain evidence which they offered at the trial.

The exception on which the defendants’ counsel mainly relied was the exclusion of evidence that the plaintiff, while in their service, sold only a certain amount of merchandise, which was *392far less than was sold by others whom they employed in the same department. But we are of opinion that evidence of this fact was not admissible on the trial of the question in issue, namely, whether the plaintiff devoted his time and attention to their service according to his best knowledge and ability. Its admission would necessarily have led to the trial of collateral questions, and to testimony as to the kinds of merchandise which he and others sold, and as to the time during which he was employed in buying goods and in managing the defendants’ woollen department — these as well as the selling of merchandise being part of the service which he undertook to perform for them — and also to a comparison of the time employed by him with the time employed by others in their service, in the single business of selling. Mere proof that he, during a specified time, sold far less in amount than others sold would have had no legal tendency to show that he did not devote his time and attention to their service, according to the best of his knowledge and ability.

There are two sufficient reasons for the exclusion of Wash-burn’s testimony that he stated to the plaintiff what was the amount of his sales and profits, and what was the amount of the sales and profits of others. First, the testimony which Washburn was permitted to give on that matter was in itself Irrelevant and inadmissible; and so would have been any further particulars concerning it. Secondly, both the testimony which was received and that which was rejected were offered for the purpose of contradicting the testimony of the plaintiff, on cross-examination, concerning the same collateral and immaterial matter; and this the law does not permit. No rule of evidence is more firmly settled.

We think that Washburn was rightly refused permission to state the reason why the defendants discharged the plaintiff from their service. The motive which actually caused them to do this was immaterial, if they had a justifiable cause for doing it. And that was to be determined by the jury, on all the evidence before them. Testimony that the defendants dismissed the plaintiff on the charge that he had broken his engagement *393would not have been legal evidence that he had broken it, nor would it have strengthened the other evidence which they had introduced in their defence. And taking the whole of Foque’s testimony, it furnished no ground for suspicion that the plaintiff was really dismissed for any other cause than an alleged breach of his agreement. There was nothing in it which the offered testimony of Washburn would have rebutted.

Exceptions overruled.