Many interesting problems present themselves when a house has to be built or rented. There is often opportunity for some choice of material in walls or roof, and some peculiarities to be considered. Are the top rooms of a thatched cottage warmer or colder than the top rooms of a house covered with slates? Is a wooden or an iron building warmer? What difference does it make if the iron building is lined with wood? If the iron walls were twice as thick, what would be the effect inside the room? Would the walls of such a building be always dry inside? It sometimes happens that the end wall of a row of houses is covered with slates to preserve it from the effects of storms of wind and rain; will that inside wall be always dry? But the housewife is probably more interested in those articles in use in the house which it is her business to provide. Shall the stoves be of slate or iron? In olden days warming-pans were made of copper. What change in the manner of use justifies making them of earthenware or India-rubber? The slow transmission of heat through thick woollen materials has been applied to the construction of Norwegian cooking-stoves (Fig. 5). These stoves consist of a wooden box, lined with well-padded felt. The cooking vessels are of metal; the food when at boiling point is placed in these vessels and the lids put on, a thick padded felt is placed on the vessels and entirely fills the wooden lid of the box which is then closed; the heat is preserved so that the cooking is continued without further attention. Would it be possible to use the Norwegian stove as a refrigerator? Would it keep an ice pudding cold without any alteration? In connection with this we may ask why freezing machines have the inner vessel in which the freezing takes place of zinc, and the outer vessel which contains the ice and salt of wood? What would be the effect of interchanging the materials? [Illustration: FIG. 5.] It is possible that the excellence of some continental cookery is due to the extensive use on the continent of earthenware cooking utensils through which heat passes very slowly. The growing fashion of using enamelled cooking vessels must have some effect on the food cooked in them as heat certainly passes quickly through them. Reference has been made to them simply to demonstrate the universality of the application of physical laws, and we may now return to the house and its arrangement for the comfort of the inmates. METHODS OF DOMESTIC HEATING