delivered the opinion of the Court. The inhabitants of the town of Lexington are undoubtedly bound by their act of incorporation of 1712, by which they were set off from the town of Cambridge, to pay their proportion of supporting the great bridge, according to the terms of the act, and the articles of agreement referred to and recited in it, and the question is upon the construction of the act, to ascertain what those terms were.

Previously to this act of incorporation, in 1699, an act was passed, providing for the rebuilding of what was then called the great bridge over Charles river in Cambridge, which provided among other things, that after the bridge should be re built and finished, it should from time to time be repaired and maintained at the charge of the towns of Cambridge and Newton, in the proportion of two thirds to Cambridge, and one third to Newton. It appears, however, that although this duty was imposed on Cambridge and Newton, the Province did something afterwards for their relief. In 1730, Lexing.ton and five other towns (probably those which had been set off from Cambridge and Newton) petitioned for such relief, but it was not then granted. In 1732, the Province granted ¿E300 towards these expenses ; and in 1734, they granted 3000 acres of land to Cambridge, Lexington and Newton, to enable them to support the .great bridge for ever.

*226By force of this act of 1699, the support of this great bridge was charged upon the towns of Cambridge and Newton, both having at an earlier period constituted one town, and this obligation existed, at the time that Lexington was set off from Cambridge into a separate town. By this act of incorporation they were set off into a distinct town upon such terms as they and the town of Cambridge had agreed upon ; that is to say, that said Precinct, when made a township, should bear such a part of the two thirds of the charge of the great bridge as should be according to their proportion with Cambridge of the Province tax, and should annually pay the treasurer of Cambridge their part of the charges as aforesaid. By their acceptance of this act of incorporation, the town of Lexington agreed to this condition, and became bound to comply with it. From these provisions, it appears obvious, that the, parties regarded this duty as an extraordinary one, created by a special act, and not depending upon the general laws and policy of the government, and that they intended, that whilst each town, after the division, should become subject to the common and ordinary duties and liabilities of municipal corporations, this obligation should remain common to both, according to their respective ability, as expressed by their respective proportions paid to the Province tax ; in other words, to be borne by the inhabitants of both towns, in the same manner as if they had not been divided.

Then the question is, what was the effect of the act of 1781, exempting Newton from the payment of one third of the expense of repairing this bridge, upon the relative rights and obligations of Cambridge and Lexington ? The defendant town contends, that in no event were they liable, by their act of incorporation, to pay more than two thirds of the expenses of maintaining this bridge ; that if the exemption of Newton threw an obligation upon Cambridge to pay the other third, it was a new duty, created after the separation, for which they could not be responsible, any more than if an act had passed requiring Cambridge to build a new bridge. On the contrary, it is contended by the plaintiff town, that the words “ the two thirds,” in the act, were not intended to limit the proportion which Lexington should pay, that it was descriptive *227of the duty that then rested on the town of Cambridge, before the separation, which was then only two thirds, that the substance of the agreement was, that Lexington should bear her proportion of that duty, that it was a duty created before the separation, that this was understood and intended to be the effect of the act of 1781, exempting Newton, and was so assented to by Lexington, and that this is proved by their actual payment of their proportion of these expenses according to this exposition, for half a century from the passing of the act.

It is conceded that from 1781, for fifty years, Lexington paid to Cambridge her proportion of the whole of these expenses. The suggestion that this was done without knowing that she was paying more than her proportion of two thirds, seems unfounded, and the presumption is violent, that Lexington must, from time to time, through her proper auditing and accounting officers, have examined the accounts of these repairs, and through them must have had notice that she was paying a proportion of the whole instead of two thirds. Such a payment, uninterruptedly, for such a length of time, is strong evidence of a subsisting debt or duty ; but the question is, what legal effect can be given to this fact, or rather what species of legal presumption does it tend to support, which shall establish a subsisting and continuing obligation on the part of Lexington to continue such payment. It may be regarded in two points of view ; either, 1. as a contemporaneous construction of the act of 1781, virtually recognising the duty of Lexington to unite with Cambridge in bearing this obligation as before, to the full extent of the liability of Cambridge, in regard to this bridge ; or 2. as evidence of a new and original agreement between Cambridge and Lexington, with the sanction of the Legislature, upon the petition of the town of Newton to be absolved from her obligation, by which Cambridge and Lexington consented to assume it, and in consideration of which the act was passed.

1. The act of 1781, which is very short, is rather peculiar in its provisions. It does not enact in direct terms, that Newton shall be exempted from paying one third of these expenses, it does not in terms direct how the same third shall after-wards be paid. It recites, that the General Court, in 1699, *228thought fit to pass an act for the purpose of supporting and maintaining Cambridge bridge, and by that act, subjected Newton to one third of the charge, &c., and it then proceeds to repeal that part of the act, that subjects the town of Newton to any part of such charge. It holds the town of Newton liable to pay one third of the repairs, then to be made, agreeable to an agreement entered into between the selectmen ot the towns of Cambridge, Newton and Lexington in May then preceding. This clause tacitly recognises the pre-existing obligation of these three towns to make these repairs. The act itself does not direct how the repairs shall be afterwards made ; that is left to implication. But by referring to the duty as created by the act of 1699, the implication is, that it was to continue to be supported as provided for by that act, except so far as it was affected by the repeal in relation to Newton. .But as the duty was laid on Cambridge and Newton jointly, when Lexington was part of Cambridge, would it be a forced construction, that when Newton was released, it was understood that the duty would remain on Cambridge, as she was when the duty was created, including Lexington, and that it would now rest on Cambridge and Lexington, although for general purpose es they had been formed into two corporations, subject to í common liability in regard to this duty ? The fact that the parties directly and adversely interested, immediately proceed ed to act in conformity to this view, and so continued for half a century, is a contemporaneous construction, affording strong evidence, that such was the intent of the legislature and of the parties, and that the act was passed with their assent and acquiescence, and was to be so construed. The reason assigned for absolving Newton, in the act, is, that whereas she had at the time of passing the former act (1699) no part of any great bridge to support, whereas now (1781) she had half of five bridges over Charles river to support, &c. At this time, Lexington had no great bridge to support, and therefore it might be thought reasonable that she should bear her proportion with Cambridge, of the burden originally common to both.

Further, it is to be observed, that this being a bridge cvei navigable waters, (Commonwealth v. Charlestown, 1 Pick *229180,) and also being a bridge, the erection and maintenance of which was specially provided for, by legislative acts, (Si. 5 Will. Sf Mary, § 1, Ancient Chart. 268,) it was not one which the town of Cambridge was bound to support, under the.general obligation of towns to maintain highways. The obligation, therefore, if any, which devolved on Cambridge, to pay the whole, in 1781., when Newton was exempted from paying one third, must have been considered by the legislature to be imposed in virtue of the duty created by the act of 1699, when Cambridge and Lexington were one town. But the act of 1699 subjected Cambridge, in terms, only to two thirds of those expenses. Any exposition or construction of the act of 1781, which would give it the effect to charge Cambridge with the whole of these expenses on the repeal of that part of the act, which subjected Newton to one third, would in like manner charge the inhabitants of Lexington with their proportion of the whole as they were liable to the like proportion of two thirds before. That Cambridge so understood the act is manifest from the fact, that they forthwith assumed the whole expense and have borne it ever since, and that Lexington so understood it and acquiesced in it, is alike manifest from the fact, that they thenceforth assumed, and paid without objection for a long time, their proportion of the whole of these expenses.

It is to be considered that we are dealing, with facts, beyond living memory, that the rights of parties, and their understandings and contracts, must be judged by their acts, especially where they are adverse to their interests, uniform, and of long continuance. With these considerations in view, it is reasonable to conclude, that when this act was passed, absolving Newton in consideration "of her now having other expensive bridges to support, it was intended to place this obligation on Cambridge and Lexington, the latter having no great bridge to support, and they being as one town jointly liable in 1699, when the original obligation was created, and that it was done in this mode, by repealing that part of the act of 1699 which charged Newton jointly with Cambridge, for the purpose of leaving the burden of the whole to rest on Cambridge by force of the act of 1699, so as to make it take effect at a time an*230terior to the incorporation of Lexington, and thus by force of the act of incorporation, to subject that town ,to her share of this burden. That such was the real purpose and intent of this act, that Cambridge and Lexington both so understood and assented to it, is manifest from the fact, that they both proceeded to act in conformity with this construction, until a period when it may be presumed that all living memory of the actual circumstances of the transaction had become obliterated. In all ancient instruments and transactions, where doubtful words are used, where the purpose and intent are obscurely expressed, the acts and conduct of the parties, immediately following, are to be regarded as the best expositors. Livingston v. Tenbroeck, 16 Johns. R. 14. It is upon this ground, that possession, occupation, and use are allowed to have so prevailing an influence, in all old deeds, grants and conveyances.

2. But if this construction were more doubtful, the Court would be strongly inclined to the opinion, that the payment for fifty years, would of itself afford presumptive evidence, in connexion with the circumstances of the case, of a new and original agreement, of which the evidence is now lost by time and accident, by which Lexington undertook to pay to Cambridge the same proportion of the whole expense of supporting and repairing this bridge, as she had formerly paiS of two thirds of the same expense, before Newton was released.

The long acquiescence of a party, in an adverse claim of right, the long-continued performance of a duty to another, not only without resistance but without objection* is a strong ground upon which to establish rights and duties ; and much of the security of property and of the peace of society, is founded upon a steady adherence to this salutary rule. It is founded on the strictest course of legal reasoning, inasmuch as it would be contrary to all experience for a party long to con tinue to pay money, or perform any other onerous duty to another, unless in pursuance of some contract or other legal obligation.

Defendants defaulted.