The opinion of the Court was read at the ensuing Septembci term as drawn up by
Mellen C. J.The plaintiffs contend that ever since the act of 1820 was passed, they have been entitled to boomage for logs at the rate of fifty cents per thousand, because, as that act contains no proviso, as the other acts do, the legislature had no constitutional power to reduce the amount of boomage thereby granted to the corporation. The correctness of this position the defendants deny; and whether the legislature had such right is one of the questions to be decided. It is a correct principle that a grant is a contract; and that rights absolutely vested under it, cannot bo divested by an act of the legislature; to this point we will merely cite Fletcher v. Peck, 6 Cranch 87; State of New Jersey v. Wilson, 7 Cranch 164; King v. Dedham Bank, 15 Mass. 454 ; Foster & al. v. Essex Bank, 16 Mass. 270; Charles river bridge v. Warren bridge, 7 Pick. 344. But it is urged as a settled principle, and hot denied, that where by the terms of a charter the legislature reserve to themselves the right to declare it void or revoke it, if certain events should take place, or to modify the terms of it in certain particulars according to their pleasure, they have a constitutional right so to do; because the charter is accepted on these conditions : and the principle hero applies, cujus est dare, ejus est disponere. The logs, for the boomage of which the present action is brought, were boomed and secured in virtue of the act of 1812, extending the charter above the falls and bridge. As has been before observed, the same proviso is found in both the acts granting the right of maintaining *478booms to the corporation; and both acts have been accepted. Here then we are led to the inquiry,<e wliat is the legal import of the proviso in the act of 1812, and what is its effect ? Its language is, “ the fees aforesaid shall at all times hereafter, be subject to the revision and alteration of the legislature.” Does the expression refer merely to the fees particularly stated in that act ? If so, then they could ’ never be subject to the revision and alteration of the legislature but once ; and if instead of being increased to fifty cents per thousand, they had been reduced to twenty-five cents by tho act of 1820, they could never have been raised again by virtue of the proviso merely ; for on this principle the proviso would have been satisfied — have done its office, and spent all its force. Nearly at the same time, the proprietors of Saco boom were incorporated. The language of the proviso there is, “ the fees or toll shall at all times hereafter,” &e. Besides, such a construction is expressly repugnant to the language of the proviso, which is, “ the fees aforesaid shall at all times hereafter be subject to the revision and alteration of the legislature.” ' This must mean something more than one alteration. We apprehend the true construction to be more liberal than that for which the plaintiffs contend $ and in order to give effect to the plain language of the proviso, we must understand it in the same manner as though it had been this : “ provided nevertheless, that the amount of fees for stopping in said river and rafting and properly securing logs and other lumber as aforesaid, shall at all times hereafter be subject to the revision and alteration of the legislature.” Such a construction makes the language of the proviso sensible and consistent; and gives-effect to every part of it. Such, certainly, must have been the manner in which the legislature understood it, when they passed the act of March 15, 1821, as in the act of January 1820, the proviso was not inserted. In aid of our construction we may well suppose that the right of revision and alteration was reserved to the legislature, because the experiment, being a new one, and the anticipated profits uncertain,' such a power might be highly useful, if not necessary, to prevent an undue or unreasonable income to the corporation j and the frequent changes and gradual reduction, as to the amount of boumage, furnish us with proof of the wisdom of those who in*479serted this proviso in the first and second acts before mentioned. It is truo tlie same proviso is contained in the acts of 1821 and 1829 : it was probably transcribed from the former acts without any particular motive, or else from abundant caution 3 but as, in our opinion, the insertion of the proviso, in any of the acts subsequent to that of 1812, was wholly unnecessary, the omission of it in the act of 1820, could not operate as a limitation upon the constitutional power of the legislature in 1821, to reduce the boomage in question from fifty cents to forty cents per thousand; or of the legislature in 1829, to reduce it from forty to thirty cents per thousand. In the case of Holbrook v. Holbrook, 1 Pick. 254, the court observe that the general system of legislation on the subject matter, may be taken into view, to aid the construction of any one statute relating to the samo subject. In the numerous acts, establishing turnpike corporations, it will be found on examination that no right is reserved to the legislature to revise and alter the established toll at pleasure or until after a limited period. It is true they may increase the tolls without any such reservation, though not reduce them. So far as we have examined other acts granting tolls to bridge proprietors or canal proprietors, we have found no such reservation as that contained in the proviso under consideration. The natural inference from this distinguishing fact is that tlie legislature intended, in the present instance, to place the subject of fees or boomage, completely under their own control; so that at all times afterwards, they might have the undisputed power of regulating the income of the proprietors from this source, according to circumstances, by increasing or reducing the boomage. We cannot conceive that a proviso so unusual should have been introduced, to enable the legislature to make a single alteration — say, a reduction of two cents per thousand on logs, and in the same proportion on other timber and articles, and there be compelled to stop for want of authority to proceed any further. From a cursory examination of the acts of Massachusetts granting charters of tlie kinds before mentioned, it appears that no proviso of the kind in question is introduced until the year 1804, and very few are found till our own government was organized ; since which time *480it seems to have been the practice to introduce it in cases where tolls or fees are granted.
As to the boomage of all the logs boomed and received after the 21st of March, 1829, the defendants contend that the plaintiffs have no right to maintain their action, because the same were not legally surveyed, according to the provisions of the first and second sections of the act of 1829. The first section declares “that it shall not be lawful for the proprietors to ask, demand or receive the toll established by this act, of. the owners of logs, by said corporation rafted out of said booms and secured for the several owners thereof, unless said logs, after they are rafted out of said booms and secured, shall be duly surveyed by a surveyor appointed and sworn as is hereafter provided ; and a bill of the survey of said logs shall be delivered to the person receiving the same.” The second section provides for the appointment of such surveyors ánd their qualification ; which appointment is to be made by the selectmen of Brunswick and Topsham. The case finds that the logs referied to in this objection were never surveyed in the manner prescribed by the statute above mentioned; and the answer made to this objection is that the first section is unconstitutional, as it impairs the rights granted to the corporation by subjecting them to burdens and expenses, inconsistent with those rights, and, in their operation, destructive of them. By the terms of their charter, the proprietors have the control of the logs, until delivered to the owners; and a right to retain them until the toll or boomage is paid or secured to their satisfaction. They, of course, were obliged to have the logs surveyed by some person or persons, before the act of 1829 was passed, in order to ascertain the amount of toll or boomage which they had a right to demand and receive of the owners; and the report states that prior to that act “ it was the practice of the boom-master to survey the logs as they were rafted out, in order'to enable him to return an account of the quantity to the treasurer and collector, whose duty it was to collect the boomage; and no charge for such survey was made.” It is understood that the nature of the survey is such as to be attended with very little trouble; and if there formerly was any expense attending it, that expense was borne by *481the corporation. The act of 1829 has only provided, and doubtless for good reasons, that some indifferent and disinterested person or persons should make this survey; being appointed in the manner before mentioned, and acting under the sanction of an oath. It does not appear that such a survey is more troublesome or onerous to the corporation than any other, though probably it is more satisfactory, if not more correct and important; and, in order to insure such a survey, a certificate, in conformity to the act, is made a necessary preliminary to a recovery of the toll or boomago. We do not perceive how the provisions of the act now under consideration operate to destroy or impair any of the rights granted to the corporation by their charier. The cases, or several of them, cited by the counsel for the defendants, presented to the consideration of the court questions arising out of acts of the legislature, at least as liable to objection on constitutional grounds as the section of the act under examination. See also 4 Peters 514. It is not retrospective in its provisions; even if it compels the corporation to incur a small additional expense in the survey, it is no more than was required of the baidcs in procuring and using stereotype plates. Tt declares that proof of a survey, according to its provisions, shall be necessary to entitle the corporation to recover their foes. The legislature may surely prescribe what evidence shall be necessary to support actions of a particular kind ; and, if in writing, how it shall be obtained and certified. Unless an act, of the legislature, or some part of it, is evidently unconstitutional, this court would never feel at liberty to pronounce it so. The section imposes no now duty, but only requires that an existing duty shall be performed by persons of a certain character. The resolve of February 15, 1828, declared that unless tliis same corporation should, on or before the 15th day of September then next, make, erect and finish such piers and booms, at and above the carrying place in said river, between Brunswick and Topsliam, as should be adjudged, upon view by certain persons spe oially designated, sufficiently strong, substantial and extensive to stop and secure all masts, logs and other lumber floating down said river, it should be the duty of the attorney general to take legal measures for causing their charter to bn vacated; and that until *482such piers and booms should be completed, and certified to be so by such designated committee, the corporation should have no right to receive any toll or fees. Here were duties and conditions imposed, not embraced in the charter ; but the report states that pursuant to the resolve the piers and booms were completed and a cer - tificate given accordingly. The corporation considered the subject under the control and jurisdiction of the legislature, and conducted accordingly. On the whole ,we are satisfied that the objection as to the constitutionality of those parts of the act of 1829 which we have been examining cannot be sustained. On this principle it appears that nothing more was due to the -plaintiffs when the action was commenced, than the sum of seventeen dollars, which was brought into court on the common rule, and now belongs to the plaintiffs 5 ant? according to the terms of the report the verdict must be set aside and a nonsuit entered.