[ 22Z ]

a sand-bath, and the sire increased by degrees, so as to keepthe sand at last; red hot for some time. The fire being thensuffered to decay, and the vessel broken when cold, a salinematter, consisting chiefly of sal ammoniac, is found in itsupper part: under this is a dark red mass, which proves tobe cinnabar, ora combination of mercury and sulphur:at the bottom is the au rum mosaicum, a sparkling, goldcoloured, flaky mass, weighing about a twelfth part morethan the tin employed.

The gold coloured talcs, formerly mentioned, have toomuch flexibility and elasticity to be reduced into powder ofsufficient fineness for the purposes of painting: but thereis one imitation of gold, for which powders of much fine-ness are not required, and for which the talcs are betteradapted than any other material I know of, on account oftheir resistance to fire. A kind of glass, with gold colouredspangles diffused through its substance, has been muchadmired, and the preparation of it kept a secret: this ap-pearance may be communicated by the yellow talcs, bymixing them well with powdered glass and bringing themixture into fusion..

III. Gold coloured varnish or lacker.

Silver, coated with a transparent gold coloured varnish,is made to resemble gold so exactly, as wholly to supply theplace of gold in some of the works called gilt. The basisof the varnish, or what gives adhesiveness and glossiness to.the colouring matter, is a solution of lac made in spirit ofwine.

Lac or lacca is a substance collected by certain insectsin the East Indies: it is found incrustated on sticks orbranches of trees, in brittle masses of a dark red colour,which being reduced into small grains, and freed frompart of the colouring matter by infusion in water, are sold.under the name of feed lac. It is in this slate that the lac

is