It was incumbent on the plaintiffs to prove a liability on the part of the defendant to pay the tolls which they sought to recover in this action. For this purpose they relied on the implied assumpsit arising from proof that the defendant had passed their bridge without paying the usual tolls. This made out a prima facie case, and would entitle them to recover unless the defendant offered some evidence to rebut it. But it does not follow that the burden of proof was thereby shifted. On the contrary, in the absence of any matter in avoidance or discharge, the fact to be proved remained the same. By showing that certain persons were by the votes of the corporation exempt from toll, and by proof tending to show that the defendant was included among them, he only endeavored to meet and overthrow the case which the plaintiffs, by their evidence, had sought to establish. The plaintiffs averred the legal liability of the defendant to pay tolls. To this aver*132ment the evidence on both sides was directed; and as the plaintiffs affirmed it as the foundation of their claim, so they were bound to sustain it by proof in all stages of the trial.
The burden of proof and the weight of evidence are two very different things. The former remains on the party affirming a fact in support of his case, and does not change in any aspect of the cause; the latter shifts from side to side in the progress of a trial, according to the nature and strength of the proofs offered in support or denial of the main fact to be established. In the case at bar, the averment which the plaintiff was bound to maintain was, that the defendant was legally liable for the payment of tolls. In answer to this, the defendant did not aver any new and distinct fact; such as payment, accord and satisfaction, or release; but offered evidence to rebut this alleged legal liability. By so doing, he did not assume the burden of proof, which still rested on the plaintiffs ; but only sought to rebut the prima facie case which the plaintiffs had proved against him. The ruling of the court on this point was therefore right.
The evidence, that other persons going to certain premises in Dracut were allowed to pass the bridge free of toll, was clearly competent; because it was in the nature of an admission by the defendants that the estate in Dracut to which these persons were going was included in the vote of the corporation exempting certain territory and persons residing thereon from liability to tolls. It being admitted that the defendant and members of his family frequently passed over the bridge to the same premises, the evidence had a direct bearing on the question at issue between the parties. Exceptions overruled.