Section 30. Money voted by such corporation may be assessed on the pews in its meeting house, and the assessment may be committed to its treasurer, who shall forthwith give notice by posting an advertisement on the principal outer door of the meeting house, stating the making of such assessment and the date of its delivery to him; and if any part of the taxes so assessed remains unpaid for three months thereafter, the treasurer shall forthwith collect the same by sales by public auction of the pews upon which such taxes remain unpaid.