CEME

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beautifully white, and dries almost transparent. Papers pastedtogether by means of this cement will sooner separate in their ownsubstance than at the joining, which makes it useful in the prepara-tion of curious paper articles, as tea-trays, ladies' dressing-boxes,and other articles that require layers of paper to be cementedtogether.

Iron Cement is formed of the borings of cast-iron guns, or turningsof cast-iron, which should be clean and free from dust until used.By slight pounding or triturating they are broken, but not powdered,and then coarsely sifted. At the time of using they are to be mixedwith powdered sal ammoniac and sulphur, and slightly moistenedwith water ; when the composition must be rammed, or chaulkedinto the joints, with a blunt chaulking chisel and hammer, and thejoints screwed up by its bolts as tightly as possible. No more of thiscement must be made than can be used at one time, because it soonspoils; but if good, it will become as hard as the iron itself in a fewdays; gij of sal ammoniac, and jj of sulphur is sufficient for Ibv ofiron borings.

Isinglass or Turkish Cement, is made by dissolving mastich in as muchspirit of wine as will suffice to render it liquid ; in another vesseldissolve as much isinglass, which has been previously soaked inwater till it is swollen and soft, in brandy, as will make jij by mea-sure of strong glue, and add two small bits of gum galbanum, orammoniacum, which must be rubbed, or ground, till they are dis-solved ; then mix the whole with a sufficient heat; keep it in aphial stopped, and when it is to be used set in hot water.

Or, to six parts of yellow potters' clay, add one part of steel filings,and a sufficient quantity of oil. Make the paste of the consistenceof glaziers' putty.

Cement for Metals. Take of gum mastich gr. x, and rectified spiritof wine Jij. Add Jij of strong isinglass glue, made with brandy,and gr. x of the true gum ammoniac. Dissolve all together, andkeep it stopped in a phial. When intended to be used, set it inwarm water.

Mahogany-coloured Cement. Melt together Jij of bees' wax, and Jssof Indian red, and a small quantity of yellow ochre, to bring it tothe proper colour.

Parkers Cement is made of very argillaceous limestone burnt in coni-cal kilns, with a continued fire of pit-coal, in the same manner asother limestone; but if the heat be so great as to cause a commence-ment of fusion in the cement, it will be totally spoiled. It is re-duced to an impalpable powder by grinding as soon as it is burnt,and is sent away in barrels, well closed. The above is much used