One oz. of potash, 2 oz. of whitening, and a square of yellow soap, cut into small pieces; boil all together in a saucepan, until it begins to thicken; apply this with a large brush to the marble. If the marble is very dirty, let it remain on all night; if not, one hour will be sufficient. Then wash it carefully oft' with plenty of cold water and a sponge. Take care the mixture is not applied too hot. Or: -

Equal quantities of soft soap and pearlash.

Put the soap and pearlash on the chimney-piece with a soft flannel; let it lie on it for a few minutes. Wash it off with warm water, not too hot; wash it over a second time with cold spring water. Acids act on marble. Marble is itself com- posed of carbonate of lime - that is, it is a compound of carbonic acid and lime. Now the carbonic acid has a comparatively weak affinity for lime, and most other acids will prevail over it and take its place when brought into contact with it; thus destroying the texture of the stone, liberating the carbonic acid, and leaving some salt of lime, in the form of a white powder, in its place.

When marble has had its polished surface eroded by acids - and even lemon juice or vinegar will do this readily - the only mode of reparation is to have the marble again polished by the use of polishing powders, such as emery.

Neither spirits nor water produce any permanent effect on marble, but fixed oils and grease soak into its substance, and it is impossible to remove them, as any agent potent enough to act on the grease will also destroy the texture of the marble. A portion of the grease may be extracted by covering with fuller's earth or pipeclay. But marble should be carefully preserved from contact with grease or oil.