it must contain so much moisture as to become, by beating, a solid mass, adhering in all its parts, and not remain crumbling, that will properly set as mortar. If there be too little moisture at first, it will remain a powder; if there be too much, it will become a soft mortar. Lime is of no use, mixed with clay or vegetable earths; which, if well beaten, are stronger without it. 1143. _To cure Damp Walls._--Boil two quarts of tar, with two ounces of kitchen-grease, for a quarter of an hour, in an iron pot. Add some of this tar to a mixture of slaked lime and powdered glass, which have passed through a flour-sieve, and been completely dried over the fire in an iron pot, in the proportion of two parts of lime and one of glass, till the mixture becomes of the consistence of thin plaster. The cement must be used immediately after being mixed, and therefore it is proper not to mix more of it than will coat one square foot of wall, since it quickly becomes too hard for use; and care must be taken to prevent any moisture from mixing with the cement. For a wall merely damp, a coating one-eighth of an inch thick is sufficient; but if the wall is wet, there must be a second coat. Plaster made of lime, hair, and plaster of Paris, may afterwards be laid on as a cement. The cement above described will unite the parts of Portland stone or marble, so as to make them as durable as they were prior to the fracture. 1144. _To increase the Durability of Tiles for covering Buildings._--The following composition has been found to be of extraordinary durability, as a glazing or varnish for tiles. No sort of weather, even for a considerable length of time, has had any effect upon it. It prevents that absorption of water, by which common tiles are rendered liable to crumble into dust, hinders the shivering of tiles, and gives to red bricks a soft lustre, by which their appearance is much improved.