SEC. 14. No wagon, dray, cart or other vehicle loaded, in whole or in part, with gunpowder or gun-cotton, shall be permitted to stand or remain on any street, alley, highway or place in said city, except when unavoidably detained, and every magazine, safe, box or keg used for storing or transporting, and all vehicles employed in hauling gunpowder or gun-cotton within the city, shall have the word “Powder” painted upon both sides of the same in large letters.