The portions preferred are the following, viz.—one pound of gutta-percha, six ounces of sulphur, and from six to eight ounces of either magnesia or lime, or a carbonate, or a sulphate of magnesia or of lime, or calcined French chalk, or other magnesian earth. Instead of using the specified proportion of the magnesia or lime, or of the carbonate or sulphate of magnesia or lime, or of calcine French chalk or other magnesian earth, the same proportion of any two or more of these substances combined, may be employed, care being taken that the quantity of this third ingredient in the composition does not vary from the proportion of six or eight ounces. These proportions may, however, be slightly varied, without materially changing the result. To the composition above specified, a fourth ingredient may be added, viz., gum shellac, by which a still better article will be produced—the body thus obtained being stronger and more easily worked. The quantity of shellac, in such case, should be about four ounces to every pound of gutta-percha. Resin, oxide or salts of lead or zinc, of all colors, and other like substances, both mineral and vegetable may be added, in small quantities, to either of the above compositions, for the purposes before stated with respect to the India-rubber composition. The compounds described may be mixed by a masticating machine or other means, until the several ingredients are thoroughly incorporated. The mineral ingredients should be finely divided, and good results are obtained by reducing them before mixture, to an impalpable powder. When rolled or moulded, the compounds are then to be “cured.” This is effected by exposing the compound to a high degree of artificial heat, using for this purpose either steam, hot water, or hot air. The degree of heat to which this compound is to be exposed, and the duration of its exposure, will depend somewhat upon the size and thickness of the article; but in ordinary cases the heat should be raised to about 260° or 270°, Fah., and the compound exposed to such heat for about four hours; as a general rule, however, it may be stated that the heat should range from 250° to 300°, Fah., and the time of exposure from two to six hours. The compounds or compositions by undergoing this heating or curing operation, will become of a hard, stiff character, in many respects resembling tortoise-shell, horn, bone, ivory, and jet. In the compounds described as compositions of caoutchouc, considerable proportions of gutta-percha may be substituted for caoutchouc (rubber) without injury; and, in the compounds described as compositions of gutta-percha, considerable proportions of caoutchouc may also be substituted for gutta-percha without injury * * * *