Four different ways used in France for securing dry cellar walls are shown in Fig. 11. The heavy black line represents the damp course, which, when added to the effect of the interwall space, which is shown in all the drawings but the first, and there replaced by a deep drain, insures absolute freedom from all moisture within the cellar. Figure 12 shows sections recommended by Dr. George M. Price, and indicates clearly the location of the damp course. _The cellar floor._ The floor of the cellar, in the same way, must be kept from dampness, and this is best done by covering the cellar floor with a layer of concrete, one part cement, three parts sand, and six parts broken stone; or, one part cement and eight parts gravel may be used. Care should be taken, however, that the gravel does not contain an excess of sand, and it is always well in using gravel for concrete to check the proportion of these two materials. This may be done as follows: Sift the gravel through an ash sieve so that it is free from sand; fill a ten-quart pail even full with the gravel and then pour in water to the top of the pail, keeping account of the amount of water poured in. This volume of water gives the proper amount of sand to use with the gravel for concrete, and if more sand than this was present in the original gravel, it should be sifted out until the proper proportion is reached. Concrete is not water-tight, and the concrete floor of the cellar must be treated in some way to prevent water or moisture rising through this floor. One method is to cover the concrete thus laid with a denser mixture of cement and sand, put on three fourths of an inch thick, and made by mixing equal parts of sand and cement; or the asphalt layer already referred to in the cellar walls may be carried across the cellar, putting, as before, a paint layer on the concrete, then paper, then another paint layer, making it continuous and without a break from outside to outside. On top of this, to prevent wear and tear, a floor of brick, laid flat, or a two-inch layer of concrete may be laid. _Cellar ventilation._ The great importance of the cellar as that part of the house where, if anywhere, unhealthy conditions exist, justifies this prolonged discussion, and before leaving the subject, ventilation in the cellar should receive a word of encouragement. Too many cellars are damper than need be, are musty and close, full of odors of decaying vegetables and rotting wood, entirely from lack of ventilation. The cellar windows are small and always, closed. The cellar door is seldom opened, and never with the idea of admitting air. The impression on entering such a cellar is of a tomb.