Waterproofing Walls.--In many badly constructed houses with thin walls there is a tendency for damp to make its way into the interior. Several remedies for this inconvenience have been published at various times. The following procedure is described by a German paper as a reliable means of drying damp walls. The wall, or that part of it which is damp, is freed from its plaster until the bricks or stones are laid bare, next further cleaned off with a stiff broom, and then covered with the mass prepared as below, and dry river-sand thrown on as a covering. Heat 1 cwt. of tar to boiling-point in a pot, best in the open air; keep boiling gently, and mix gradually 3½ lb. of lard with it. After some more stirring, 8 lb. of fine brickdust are successively put into the liquid, and moved about until thoroughly disintegrated, which has been effected when, on dipping in and withdrawing a stick, no lumps adhere to it. The fire under the pot is then reduced, merely keeping the mass hot, which in that state is applied to the wall. This part of the work, as well as the throwing on of the river-sand against the tarred surface, must be done with the trowel quickly and with sufficient force. It must be continued until the whole wall is covered both with the tar mixture and the sand. The tar must not be allowed to get cold, nor must the smallest possible spot be left uncovered, as otherwise damp would show itself again in such places, and where no sand has been thrown the following coat of plaster would not stick. When the tar covering has become cold and hard, the usual or gypsum coating may be applied. It is asserted that, if this covering has been properly dried, even in underground rooms, not a sign of dampness will be perceived. About 300 sq. ft. may be covered with the quantities above stated. An excellent asphalte or mortar for waterproofing damp walls or other surfaces is the following patented composition:--Coal tar is the basis, to which clay, asphalte, rosin, litharge, and sand are added. It is applied cold, and is extremely tenacious and weather-resisting. The area to be covered is first dried and cleaned, then primed with hot roofing varnish--chiefly tar. The mortar is then laid on cold with trowels, leaving a coat ⅜ in. thick. A large area is then coated with varnish and sprinkled over with rough sand. To frost or rain this mortar is impervious. The cost is 5_d._ per sq. ft., and for large quantities 4_d._ In the case of stone walls the following ingredients, melted and mixed together, and applied hot to the surface of stone, will prevent all damp from entering, and vegetable substance from growing upon it. 1½ lb. rosin, 1 lb. Russian tallow, 1 qt. linseed-oil. This simple remedy has been proved upon a piece of very porous stone made into the form of a basin; two coats of this liquid, on being applied, caused it to hold water as well as any earthenware vessel.