Smoke defaces, disfigures or destroys buildings and restricts the styles of architecture. The sulphuric acid particularly corrodes or disintegrates practically all kinds of building materials (slate and granite possibly excepted). Marble tends first to turn green and then black; limestone deteriorates very rapidly, turning to gypsum owing to its great affinity for sulphur. The absorption of sulphur causes the stone to expand, thus rendering it soluble and powdery so that particles are constantly washed or blown away. The very best stone obtainable was used in the new additions to the House of Parliament in London, and every care suggested by modern science was taken to preserve the materials, yet the buildings were much eroded after a few years. One of the worst aspects of the smoke nuisance is the insidiously destructive influence of smoke on ancient buildings, relics or monuments. Smoke thus not only shortens the life of building materials, but it destroys the force of expression of the architecture so that buildings are reduced to a shabby mass of begrimed masonry. The sharp outstanding moldings, designs, friezes, cornices, ornaments and carvings--the essentially artistic in architectural construction--are not only rapidly eroded but they are obliterated by the dense deposit of tarry soot, or rendered invisible because of the diminished illumination caused by the murky palls of smoke that hang over our cities. In the city of London 650 tons of soot have been deposited per square mile of ground surface, and soot deposits 3/4 inch thick have been scraped from cornice projections. The beauty of the architectural views consists in the distinctness of the outlines. Soot deposits conceal the artistic effects not only on stone and brick but also on wood. The difficulty cannot be entirely overcome by cleaning, because cleaning tends to remove the sharp edges and outlines. Moreover, preservatives for water proofing often leave an unpleasant color and frequently are not effective unless 18 or 20 coats are applied (for example of baryta-water). The ornamentation of city buildings is thus seriously restricted, while the preservation of historical landmarks is jeopardized by smoke pollution. Smoke and architectural embellishment are irreconcilable enemies.