The influence of smoke on metal work is equally pernicious. The sulphuretted hydrogen in smoke blackens, disfigures or tarnishes nearly all metals. Copper and bronze rapidly darken, iron rapidly corrodes, aluminum is affected by vapors and acids, many metals become pitted from electro-chemical action, and even gold or gilded articles become dull. Gilt titles on books will fade in the city while retaining their luster in the country. Bright and uneven metallic surfaces may also become coated with a mottled, sooty smear. To keep sign plates on any metal work bright and shiny requires constant work in smoky cities. The protective coatings used are not entirely satisfactory because they tend to crack or to peel off, or to leave pin holes. Constant cleaning entails large expense both because of the labor required and because of the wear on the metal. Rather than assume this added burden of expense merchants in smoky cities tend to minimize the use of brilliant metallic ornaments. In consequence such cities often lack that polished metallic splendor which is one of the charms of the tourist cities of the earth. Outdoor statuary in metal or stone in smoky cities suffers from all the disadvantages affecting buildings and metal work. The bituminous deposits cannot be removed by washing, and statues can only be protected by layers of water proofing. But even then ugly layers of grime will cover the exterior and render unsightly some of our best treasures of municipal art. The possibilities of landscape or decorative gardening are also artificially restricted in a smoky atmosphere. Cloudiness as such is one of the most important items in agricultural climatology. But in addition to this there are many shrubs and trees which do not thrive in smoke--rhododendrons, conifers, evergreens--while the beauty of all trees, shrubs and flowers is marred by deposits of smoky opacity. In consequence of the above artistic limitations, the artistic education available not only for the masses but particularly for students of art in smoky cities, is necessarily restricted. Their first, and sometimes only, artistic impressions are derived from an artistically limited and ultra-utilitarian environment, and from besmirched and sordid surroundings instead of from a clear, clean atmosphere of artistic excellence.