By the fifteenth section of the charter of the city, (St. 1821, c. 110,) all the powers, which were by law vested in the town of Boston, are vested in the mayor and aldermen, and common council of the city, and they have power to make all such needful and salutary by-laws as towns may make, and annex penalties, not exceeding $20, for the breach of the same, which shall be in force from and after the time therein limited, without the sanction or confirmation of any court, or other authority whatsoever; provided that such by-laws shall not be repugnant to the constitution and laws of this Commonwealth. And the city council shall have power to lay and assess taxes. The power given to towns to make by-laws is m the Rev. Sts. c. 15, § 13, for the managing of the prudential affairs of the town ; which, however, are to be approved by the court of common pleas. These by-laws, if reasonable, have as full force, as if they were made by the legislature; and it is for the court to decide whether they are reasonable, or not. Commonwealth v. Worcester, 3 Pick. 473. If unreasonable, they are void. Vandine’s case, 6 Pick. 191.
Anciently the law provided that a main drain or common sewer might be laid by an individual, at his own expense, and that those who should enter their particular drains into such main drain, should be obliged to pay, according to the judgment of the selectmen or a major part of them ; saving to the aggrieved party a right to appeal to the court of sessions. Sts 8 Ann, c. 2, and 3 Geo. III. A no. Chart. 389. 652. And *136substantially the same provisions were contained in St. 1796, c. 47.
The mayor and aldermen derive their authority from the city charter ; and by the ordinance of the city, passed February 13th, 1834, it is provided that the city shall thereafter construct and own the common sewers, and assess upon those individuals, who enter their particular drains into the same, their proportion of the expense of making the common sewer, having reference always to the last valuation in the assessors’ books previous to the expenditure.
It appears that the city laid the common sewer from a place in Pinckney Street, to the northward of the defendant’s land, through Charles Street, in 1834, and that, at the request of the defendant and others, the city continued the same to the eastward of the defendant’s land. The defendant built a house on his land between February and October, 1834, and entered his particular drain into the Pinckney Street common sewer, in that part which was laid in 1834, and on the 25th of October, 1834, he conveyed the house and land to Mrs. Foster. The assessment upon the defendant was made according to the vote of the 5th of February, 1838. At the time of this assessment, there were vacant lots in both streets through which the common sewer extends. No assessments, however, were made on those lots, but they were reserved to be made when the lots should be built upon, and drains therefrom should be entered into the common sewer. And when built upon, the assessments have been, as in other like cases, such as would have been charged, if they had been built upon when the common sewer was made.
The amount, which the owner of the land should pay towards the cost of the main drain, should be settled at the time of its construction ; and we think the intent was to" prescribe a certain rule, by which the amount of the construction should be ascertained, rather than to have it left to an indefinite and final discretion of the city officers. The last valuation in the assessors’ books, previous to the expenditure, was the basis upon which (he assessment should be laid. Provision was then made for the payment or reimbursement to the city for the whole cost of the *137common sewer. But the assessment, in the case at bar, has not been made according to the valuation of the defendant’s land next before the expenditure, which was in 1834, but upon such sum or capital as the mayor and aldermen supposed the land would have been then assessed, if there had been a house upon the land at that time. The assessment was not made until 1838. We think, that such an assessment is not according to the true intent of the ordinance, even if the ordinance itself were valid.
But is the ordinance reasonable and just ? We are constrained to answer this question in the negative.
It is better, without doubt, that the city should do the work, and that the mayor and aldermen should judge when and where a common sewer should be made. If it were left to the individual abutters to build the part against their respective lots, he expense might not fall equally ; for some might be obliged to carry the sewer through ledges and rocks, at great cost, while others, at a trifling expense, would go through a loose soil. It is better for the city to construct and to own it. And it must be considered as reasonable, that the charge should fall upon the lots abutting, which would have the privilege of entering particular drains from the respective lots into the main drain or common sewer. The right and privilege would become appurtenant to the several lots, and their value would thereby be increased probably quite as much as the amount which should be required to be paid towards the general expenditure. Thus no loss would fall upon the owners of the land. It might happen that some of the owners of vacant lots would not at present want to have a common sewer built, while other owners, having houses on their lots, would consider such an accomodation to be absolutely necessary. Let the mayor and aldermen then judge when and where the public convenience requires such main drains. There is as much reason to subject the owners of the land abutting to contribution to this expenditure, as there is to oblige them to páve the foot-ways in front of their grounds, or to keep the same in repair, when the city shall pave the streets adjoining. It should be a charge upon the land, just as is the requisition on the owners of land abutting on streets to clear away the snow *138at their own expense, which has been determined to be a reasonable provision. Goddard's case, 16 Pick. 504. It is a charge upon real estate thus situated, and requisite for the comfort and convenience of all the citizens. But how shall it be apportioned ? Shall the owner of the lot next to the outlet be, in any event, held to contribute more than the owner of the lot 600 feet above, if the former lot should have a house upon "t, and the latter should be vacant ? We think not.
Suppose A. owns a lot next to the outlet at Charles Street, of the value of $ 1,000, which, with the house upon it, is valued at $10,000, and that B. has a lot of the same dimensions, 600 feet from Charles Street, valued at $ 1,000. By the ordinance, the contribution should be made according to the valuation of these estates in the books of the assessors. The owner of one lot would be held to pay ten times as much as the other. The apportionment should be made upon the value of the land independently of the buildings, and should be settled in the time of the transaction, so that the city would neither gain nor lose by the work, and the rights and liabilities of the owners of the land be definitely ascertained.
It is not for the court to prescribe the mode by which the amount of the contribution should be ascertained ; but we are bound to say that this, which has been provided, is unequal and unreasonable, and therefore void.
We are also of opinion, that the plaintiffs cannot recover on the indebitatus count. There is nothing in the case from which the law implies a promise by the defendant to pay the plaintiffs for the benefit he may have received from their common sewer. His obligation to pay is imposed by statute or city ordinance, and not by the common law. All our statutes on this subject, from 8 Ann, c. 2, to the Rev. Sts. c. 27, inclusive, and the city ordinances also, regard contribution towards the making and repairing of common sewers as a matter in invitum; and provison is made for a tax or assessment, by public authority, upon the persons benefited. In the absence of an express promise, a legal assessment is, therefore, the only ground of legal liability to such contribution. When a new power and also the means *139of executing it are given by statute, that power can be executed in no other way. Andover & Medford Turnpike v. Gould, 6 Mass. 44. 4 Bur. 2319, 2323. 7 T. R. 627. Bangor House Proprietary v. Hinckley, 3 Fairf. 388. Moncrief v. Ely, 19 Wend. 405.
Plaintiffs nonsuit.