Limewashing- is suitable only for stables, cowsheds, fowl-houses, and out buildings. It is made by mixing freshly burnt quicklime with water to the consistence of cream; no .size is used, and it therefore easily comes off, but its value consists in its being a powerful insecticide and germicide, second only to corrosive sublimate as a disinfectant. It should be reapplied at regular periods.

Whitewashing:, although in some districts the term is applied to limewashing is in reality a totally different operation. "Whiting", finely-ground chalk, which has no disinfectant properties, is mixed with water, together with size and alum to prevent its rubbing off. It i- used for ceiliugs and rougher walls, and may be tinted by the addition of some colouring material. It is , in fact. a form of distemper.

Distemper is the name given to all colouring processs in which the pigments are mixed with size, in distinction from painting in oils, in which the vehicles ere boiled linseed-oil and turpentine. Painting in distemper is ill adapted for wood. work, to which it does not adhere well, and is practically limited to plaster, which, however, is in itself too absorbent, and requires a previous dressing with a coat of whitewash, prepared with a largei proportion of size, some slum, and soft soap. The objection to preparing the wall with a couple of coats of oil-paint is that the condensed moisture will cause the distemper to "run' , and shows that dis temper, unlike paint, is not impervious, but as absorbent as plaster or whitewash. The pigments employed, as prussian blue, indigo, ochre. umber, Venetian red,etc., are for the most part perfectly harmless, but poisonous colours are sometimes used, as emerald green, which is arsenical1 And this caution should always be borne in mind. since distemper is not so firmly adherent as oil-paint, and there is therefore a risk of the pigment becoming detached and floating in the air as dust. If desired, it may be ornamented by panels or other designs laid on in different colours by means of stencil-plates, which may be had in every kind of pattern.

1A good green may be obtained by mixing prussian or indigo blue with yellow ochre.

There are, besides, several kinds of so-called washable distempers, - such as Orr's Duresco, Ac, - non-absorbent and durable, by means of which plaster walls may be made impervious to moisture. For this purpose, however, none of them can compare with the German water-glass.

Water-glass is much used in Germany for architectural purposes and decorative art. It is a silicate of potash, which, if once allowed to dry, cannot be again dissolved save by superheated steam or very prolonged boiling, but in the gelatinous form, like size, is easily soluble in hot water. Applied as a wash to the soft stone used for architectural decorative work and the tracery of windows, it preserves it from the disintegrating action of the weather, almost without altering its colour or appearance; while for inner wall-surfaces, it constitutes a non-absorbent and therefore washable coat perfectly impervious to damp. Like distemper, it may be employed as a medium or vehicle for colour, and if mineral pigments only are used, and it is laid on a freshly-prepared surface of plaster or cement, it sinks in. producing a perfect fresco painting. The great works of Kaulbach on the walls of the museum at Berlin, and of the Pinakothek at Munich. are frescoes in water-glass, and imperishable. If the glass be dissolved with little water and used hot, the effect closely resembles that of encaustic tiles or enamel. The various application- of water-glass, alike for sanitary and decorative purposes, deserve more attention than they have yet received. There is also a soda silicate, more easily obtainable in this country, and convenient for some purposes, but from its far greater solubility little superior to ordinary distemper.

Most of the mural paintings in old churches, etc, though commonly called frescoes, are really paintings in distemper, perhaps treated with a dressing of wax for their better preservation. True frescoes are rare; in them the colours, necessarily mineral, are ground fine, mixed with water or milk of lime, and laid on a freshly-prepared surface of plaster, with which they become incorporated while it is still moist. Only a small surface can thus be painted at a time, and ones finished no subsequent touching-up or alteration is possible. Unlike distemper, the work is practically imperishable.

Oil-painting is the very best covering for walls of halls, dining-rooms, libraries, and indeed of all others. It is, however, rarely used for bedrooms, for which it would seem, on sanitary grounds, to be specially adapted, since in the event of infectious diseases occurring in the family, no stripping of the walla will be required, washing with corrosive sublimate, or even with soap and water, being sufficient for complete disinfection. Paint is absolutely impervious and non-ahaorU'iit. and easily washed. There is no danger to be feared from the use of poisonous pigments, since, unlike distemper, paint does not rub off.

The use of coloured wall-papers, though known in China from time immemorial, probably had its origin in Europe in the endeavour to find a cheap substitute for the costly tapestries which in the middle ages had taken the place of the mural paintings of the Greeks and Romans, or for the painted canvas hangings which were in vogue from the fifteenth to the seventeenth centuries. But though they have long been almost universally employed, they are, with a few exceptions of recent introduction, open to serious objections. Absorbent of moisture, retentive of dust and dirt, to say nothing of occasional infection, and (unless varnished) incapable of being washed, common wall-papers are in the highest degree in sanitary. The "flock-papers", in which shoddy dust is made to adhere more or less to the surface of patterns printed in glue, are undoubtedly the worst; happily they have of late years gone much out of favour. The pigments used are of various kinds, many of the mineral colours being poisonous; but if the surface be glazed or varnished, there is little danger to be feared from preparations of lead, cadmium, & c. It is, however, quite otherwise with the volatile compounds of mercury, antimony, and arsenic, the last being by far the most hurtful, and, formerly at any rate, most extensively employed.