In cases of necessity, and cases of emergency, where the council shall by a two-thirds vote of all the members elected declare the existence of such emergency, where an expenditure of money outside of the adopted budget may be required, such expenditure may be made, and all such expenditures shall be shown in the account books of the city clerk, except as hereinbefore provided, under the head of "emergency account," so that the clerk's books shall at all times show the expenditures made by the city outside of the adopted budget.