The answer to this petition, containing allegations and denials of matters of fact, and signed by counsel, is irregular. Tewksbury v. County Commissioners, 117 Mass. 563. Worcester & Nashua Railroad v. Railroad Commissioners, 118 Mass. 561. But by consent of the parties the case has been submitted with the same effect as if the facts stated in the report appeared by a proper return made officially by the respondents.
1. The objection “ because no grade line has been established ” is not well founded. The statutes do not require that such a line shall be formally established and defined upon the record of the proceedings, except so far as may be necessary to a proper specification of the manner in which the new highway or alteration shall be made. Gen. Sts. c. 43, § 13. So far as the rights *563or liabilities of abutters are affected by the grade of the street, they depend on and are determined by the grade as actually con structed.
2. The objection 66 that the work of laying out and grading said avenue had not been completed ” is not sustained in fact. The mere want of .railings or barriers for the protection and safety of public travel does not prevent the board from proceeding to assess the expenses. Whiting v. Mayor Aldermen of Boston, 106 Mass. 89.
3. The assessment, authorized by the St. of 1871, c. 382, § 1, is a tax, by which the expense of the laying out and construction of the way is apportioned as a public burden upon the lands especially benefited by the public improvement. The benefit or advantage to such lands is estimated only as a means of apportioning the tax and of providing a fixed limit of the amount to be assessed upon each estate. The fact of such benefit from the improvement furnishes a justification for the imposition of the tax upon a particular class of estates, instead of a levy in the general way of ordinary taxation. But such benefit conferred would not of itself alone warrant the exaction of money by way of compensation therefor. The estates are assessed, not for the benefit conferred, but for the cost of the public improvement. The essential point in the proceeding is the expenditure for a public service, for which taxation in some form is required.
The record of the board of aldermen is defective in not showing what the amount of that expense was. But the defect may and should be cured by an amendment of that record, and, upon the allegations in the answer, the agreement of the parties as to the effect thereof and the facts found at the hearing before a single justice, affords no reason why the court, in the exercise of its discretion, should order a writ of certiorari to issue. Farmington River Water Power Co. v. County Commissioners, 112 Mass. 206. Noyes v. City Council of Springfield, 116 Mass. 87. The order of the board of aldermen, taken in connection with the facts thus alleged and admitted, shows that each estate has been assessed, in proportion to the benefit and advantage received, a share of the expense of laying out and construction, not exceeding the whole amount of that expense, nor half the amount of the benefit and advantage to all the estates.
*5644. The objection that the record does not show that the mayor was present at the meeting of the board of aldermen was not insisted upon at the argument, and no objection was taken to the proceedings for want of the concurrence'of the common council. See Sts. 1852, c. 94, §§ 8, 14; 1871, c. 382, § 1; Day v. Aldermen of Springfield, 102 Mass. 310; Powers v. City Council of Springfield, 116 Mass. 84.
5. The order to collect twelve per cent, interest is not one of the errors assigned in the petition, and does not affect the validity of the order laying the assessment. Petition dismissed.