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Bread may be classed as a material by itself, as it derives certain peculiar virtues from the yeast which causes its fermentation. With certain combinations it becomes wax-like, or hard, and may be used to advantage in many repairs as well as for modelling. It has the great advantage of being easily worked and always at hand.

Celluloid is treated of in this work under the head of Artificial Ivory. It is made from gun-cotton and camphor. For full information on this subject consult Das Celluloid, or “Celluloid, its Raw Materials, Manufacture, Peculiarities, and Technical Applications, &c.,” by Dr. Fr. Böckmann, Vienna and Leipzig.

Potatoes, peeled and mashed, and kept for thirty-six hours in a mixture of eight parts of sulphuric acid to a hundred of water, and then dried and pressed, form a white, hard substance very much like ivory, or, as one may say, like white boxwood. Lehner expresses his doubt as to whether artificial meerschaum pipes were ever made of this substance, but I have seen them, and can testify that they looked like meerschaum, and certainly were much harder than bruyere, or briar-wood. Whether they will “colour” I cannot say.