Next to wood, bricks are most commonly used for building purposes, and have many advantages, among which are their handsome effect, their stability, and their being poor conductors of heat; the last mentioned is of considerable importance, since it keeps both heat and frost from rapidly permeating the interior, and as a consequence houses constructed of this material are cooler in summer and warmer in winter. Other materials occasionally used are concrete, granite, marble, and sandstone, any of which, on account of their durable character and the beauty that they lend to structures made from them, may be selected for building purposes, but inasmuch as they are rarely used in rural districts, a detailed consideration of their peculiar advantages for building purposes is not deemed here necessary. The internal wall-coating of houses deserves more consideration than is commonly accorded it, since the dyes used for coloring wall-paper and curtains in some instances contain noxious materials. Chief among those that are dangerous are the bright green pigments which commonly contain arsenic as their principal constituent; where these or other poisonous substances are employed in interior decorations the air, wherever the room is kept closed, may become more or less impregnated with poisonous gases, and serious consequences to the inmates may ensue. _Screening Indispensable to Health._--Nothing is more important in connection with house construction than having every opening thoroughly screened. We have learned that both malaria and yellow fever are transmitted always by certain kinds of mosquitoes, and it therefore, becomes a matter of the greatest importance to effectually prevent the entrance of these insects. It cannot be too strongly insisted upon that we absolutely know that the statement just made is correct, and that avoiding the diseases referred to becomes as a consequence entirely a matter of preventing the entrance of mosquitoes into houses. [Illustration: Fig. 1. ANOPHELES. (Malarial Mosquito.)] [Illustration: Fig. 2. CULEX. (Common Mosquito.)]