In case a vacancy occurs in the office of mayor of any city, by death, resignation or otherwise, the board of aldermen shall elect one of their number chairman, who shall have all the powers and perform all the duties of mayor until the vacancy shall be filled by the election and qualification of a mayor.
RSA 45:5
1871, 23:2. GL 45:12. PS 47:12. 1895, 41:4. PL 51 :5. RL 63:5.