By St. 1841, c. 115, the mayor and aldermen of the city of Boston were empowered, upon acceptance of the act, to lay, make and repair as public necessity and convenience might demand all main drains or common sewers within the municipality, which upon, construction “shall be taken and deemed to *176be the property of such town or city.” The statute having been accepted, the board whenever it adjudicated that a sewer was necessary could apportion and assess the cost of construction upon the proprietor of a particular drain which entered into the sewer either “for the draining of his cellar or land, or in obedience to the . . . ordinances of . . . the city, or who, by any more remote means, shall receive any benefit thereby for draining his cellar or land,” and the assessment constituted a lien upon the estate for one year after it was laid. St. 1841, c. 115, §§ 2, 3. Child v. Boston, 4 Allen, 41, 48.
In the expansion and development of the city additional authority was required, and by the St. of 1857, c. 225, the board of aldermen were authorized to construct sewers through the land of any persons or corporations “as they shall adjudge to be necessary for the public convenience or the public health,” and damages were to be assessed and recovered in the manner prescribed where land was taken “ for public highways or streets.” A further enlargement appears in the St. of, 1873, c. 205, § 1, which provided, that “the board of aldermen of the city of Boston may for the purposes of sewerage and drainage, take and divert the water of any streams or water courses within the limits of said city, and devote the same to the purposes aforesaid; and may take all necessary land to widen, deepen or straighten the channel of such water courses, and pave, enclose and cover the same.” And the St. of 1882, c. 164, having enacted that the words “mayor and aldermen” were to be construed as meaning "board of aldermen” this body until the St. of 1897, e. 426 was passed, continued to be invested with the plenary and exclusive powers conferred by these statutes. Gen. Sts. c. 48, §§ 1-3. St. 1869, c. 111. Pub. Sts. c. 50, § 1. St. 1892, c. 402. Allen v. Boston, 159 Mass. 324, 336. Bowditch v. Boston, 168 Mass. 239. Weed v. Boston, 172 Mass. 28. Gray v. Aldermen of Boston, 139 Mass. 328.
But a radical change followed upon the enactment of St. 1897, c. 426, §§ 2, 3, 7. The board of street commissioners, which had been established by the St. of' 1870, c. 337, and given the powers then exercised by the board of aldermen in the laying out and discontinuance of streets and ways, were thereafter to have full authority to order the construction of all public sewers, and to assess betterments, even if under the St. of 1891, c. 323, §§ 8,10, *177when ordering the location, laying out and construction of highways in accordance with the plans of a board of survey created by that statute, authority to include “the laying out of a trunk sewer ... as engineering demands shall require” seems to have been granted. Warren v. Street Commissioners, 181 Mass. 6, 7. See also St. 1894, c. 416, §§ 2, 3; St. 1902, c. 521; St. 1906, c. 393, §9.
It may be that in the absence of definitive legislative revision and consolidation of the great number of special acts governing the construction of public ways and sewers in the city, and relating to the authority of the officers charged with the supervision of the various municipal departments, there are seemingly inconsistent or contradictory expressions, when the attempt is made to construe them for the purpose of formulating a comprehensive and clear system of municipal administration. See Sts. 1885, c. 266; 1890, c. 418; 1891, c. 323; 1892, c. 402; 1894, c. 416, §§ 2, 3; 1895, c. 449, § 23; 1896, c. 204; 1897, c. 426; 1899, c. 450, § 3; 1902, c. 521; 1903, c. 268; 1906, c. 393. Ryan v. Boston, 204 Mass. 456. Commercial Wharf Co. v. Boston, 194 Mass. 460; S. C. 208 Mass. 482. Yet, the intention of the Legislature as expressed in the St. of 1897, c. 426, being unambiguous, the board of street commissioners were invested with the powers formerly exercised by the aldermen, and after the passage of this act a public sewer could not be ordered or built except upon their adjudication with the approval of the mayor. The commissioners under § 2, and not the mayor are first to decide whether a sewer shall be located and constructed, and if the approval of the mayor follows, then upon completion, the just and equitable charges for construction are to be assessed by the commissioners upon all estates specially benefited, while if he does not approve, their order is inoperative. Nor did the amendatory act of 1903, c. 268, which the plaintiff contends supports the validity of the assessment, abridge their authority. It is only after his approval, and the sewer is to be built, that the mayor under St. 1897, c. 426, § 4, as amended by St. 1903, c. 268, § 1, is to designate the superintendent of streets or such other officer as he may select to enter upon the work of construction. But whoever is designated he is to carry out and execute the order of the board of commissioners. St. 1897, c. 426, § 4. St. 1903, § 268, § 2. Although before the *178work is begun the officer thus chosen must record in the registry of deeds for the county, a statement approved by the mayor of his intention to construct the sewer, naming the street or describing the land where it is to be constructed, with his estimate of the cost, this provision only becomes applicable when the commissioners, with the mayor’s approval, have decided, that the sewer shall be built.
The construction of a sewer in the street upon which the land now owned by the plaintiff abutted having been undertaken by the mayor and superintendent of sewers without any adjudication or order of the commissioners, was unlawful and the subsequent assessment of betterments cannot cure the omission. The right to assess, and if necessary to collect by sale of the property a betterment tax, depended upon a strict compliance with the statute. Abbott v. Frost, 185 Mass. 398. Draper v. Mayor of Fall River, 185 Mass. 142. Commercial Wharf Co. v. Boston, 208 Mass. 482. And as the jurisdictional powers of the board could not be delegated their assessment did not operate as a ratification of acts originally invalid. New England Dredging Co. v. Rockport Granite Co. 149 Mass. 381, 382. Revere Water Co. v. Winthrop, 192 Mass. 455, 462. Commercial Wharf Co. v. Boston, 208 Mass. 482.
The covenant against incumbrances not having been broken when the deed of the defendants was delivered, the plaintiff has no cause of action. O’Connell v. First Parish in Malden, 204 Mass. 118. The exceptions therefore must be sustained, and under the St. of 1909, c. 236, judgment is to be entered for the defendants.
So ordered.