Celluloid, one of the most remarkable of modern inventions, bids fair to be not less extensively or variously used than vulcanized rubber. It is produced by mixing gum-camphor with gun-cotton, and subjecting the combination to a high test of pressure and heat. The result is a hard product of extraordinary toughness and elasticity. It can be made plastic again and moulded in any required form. Any color can be given to it by the use of coloring matter during the process of manufacture. It is extensively used as a substitute for ivory, which it resembles so closely that it is sometimes difficult to detect the difference. It is said to equal ivory in strength and elasticity. It has proved a good material for piano and organ keys, backs of brushes, looking-glass frames, handles for knives, forks, umbrellas, and many other articles. It is much cheaper than ivory. It is also used with much success to imitate tortoise-shell, malachite, amber, pink coral, and other costly materials. In imitation of tortoise-shell, it is made into combs, napkin-rings, match-boxes and card-cases. Imita tions of pink coral jewelry are made and sold at prices much below those of the genuine. It is also used as a substitute for porcelain in making dolls' heads. The frames of eye-glasses, opera-glasses and spectacles are made of it. More recently it has come into use in combination with linen, cotton or paper, for shirt bosoms, cuffs and collars. The material has a hard, glistening surface, like that of newly laundried linen.