MESSRS. EDITORS—Let one part of a house be built with a double wall, and let the inner one be, say three or four inches from the outer wall, made of iron, mid this space be filled during summer with alternate layers of sand and charcoal; on the top of this let ice be placed every morning, and an arrangement made to cause water to fall slowly on it. In a public house this might he done by the playing of a fountain. The charcoal, acting as a non-conductor, would preserve the coolness long, and provide the adjoining rooms; with a comfortable cool temperature. The water, being filtered, would be very pure, and could be used for various purposes. In the winter time the space might be used tor hot air. C. M. J. Philadelphia, Pa.