The conversations of the defendant with Austin were clearly competent and relevant to the issue. One of the material points, which it was necessary for the prosecution to make out, was the guilty knowledge of the defendant respecting the bills found in his possession. This is sometimes shown by evidence that the defendant has recently had other counterfeit money than that which is the subject of the indictment in his possession, and has offered to pass the same as true. Such testimony is deemed to be admissible, although it may relate to a different kind of money from that which is described in the indictment; and it is held to be relevant, although several weeks and even months may have elapsed since such previous possession or attempt to pass. Rex v. Balls, 1 Moody, C. C. 470. Regina v. Nisbett, 6 Cox, C. C. 320. Evidence of this kind, however, is not deemed to be competent unless the particular bill or note to which it relates is produced at the trial, or sufficient reason is shown for its non-production. Commonwealth v Bigelow, 8 Met. 235. If the evidence offered at the trial had been of this precise character, that is, if the testimony of Austin had been introduced for the purpose of proving that on a previous occasion the defendant had attempted to pass as true *187certain bills or notes which were false or counterfeit, it could not properly have been admitted without the production of the bills or notes, or satisfactory evidence to account for their non-production. But the testimony admitted at the trial did not tend to establish such fact. It did not show that the defendant had attempted to pass other bills than those set out in the indictment as genuine which were in fact false, or that he had them in his possession for that purpose. But it did prove an admission or confession that he was a dealer in counterfeit money, and had attempted to dispose of it as such to the witness. It cannot be doubted that a direct statement by the defendant, made previous to the transaction which forms the subject of the indictment, that he was accystomed to buy and sell counterfeit money and was familiar with different kinds of forged notes or bills, would have been admissible as tending to prove the guilty knowledge of the defendant. The testimony introduced at the trial was in effect of this character, and it was competent as a confession or admission having a material bearing on one of the issues before the jury, without the aid of extrinsic facts to render it admissible.

The letter which the defendant took from the post-office was clearly incompetent. It was in the hands of the defendant during a very brief period of time, and he neither opened nor read it. An unanswered letter is inadmissible, although the statements contained in it are well known to the party to whom it was sent; and this is held on the ground that a letter written to a party by a third person, to which no reply is made, does not show an acquiescence in the facts stated in the letter. Fearing v. Kimball, 4 Allen, 125, 128. A fortiori, a letter addressed to a person which he has not read cannot be admitted to affect him in any way. The mistake of the judge was that he permitted the letter to go to the jury after he had ruled that it was inadmissible as evidence. This was clearly irregular, but it would be an immaterial error if the contents of the letter were unim portant; but on looking at them it is clear that they were of a nature to prejudice the minds of the jury against the defendant, and to lead them to a belief that he was guilty of the crime *188charged in the indictment. Then the only question is, whether the defendant’s rights were sufficiently guarded by the direction of the judge that the letter was not evidence for the consideration of the jury, and was not to be read by them. And we are of opinion that they were not. The ruling was contradictory. If the letter was incompetent, it could not properly go to the jury ; but it being sent to them with the other documents in the case, it was in fact treated as a paper which was properly before them for consideration. In this conflict between the language and the action of the court, it is impossible to say that the jury might not have been so confused and misled as to have given some heed to the contents of the letter. When verbal testimony has been admitted in the course of a trial and subsequently on reconsideration ruled out, it is reasonable to suppose that the jury will follow the instructions of the court and give no weight to evidence which is withdrawn from their consideration, and which they are told to disregard. Tapley v. Forbes, 2 Allen, 26. But in such a case a verdict will be set aside unless it is certain that there could have been no misapprehension or mistake in the minds of the jury. Farnum v. Farnum, 13 Gray, 508. There can be no such certainty when a written document is permitted to go to the jury room after it has been rejected by the court. Upon this ground, we are of opinion that the verdict rendered against the defendant must be set aside.

Some of the court are inclined to the opinion that the evidence offered at the trial was insufficient to warrant a verdict of guilty. But as the aspect of the evidence may be essentially changed upon another trial, it is unnecessary to express a decided opinion on this point.

Exceptions sustained.