Every town annually by an article separate from the budget and all other articles in the warrant may establish a contingency fund to meet the cost of unanticipated expenses that may arise during the year. Such fund shall not exceed one per cent of the amount appropriated by the town for town purposes during the preceding year excluding capital expenditures and the amortization of debt. A detailed report of all expenditures from the contingency fund shall be made annually by the selectmen and published with their report.