With the introduction of ramie, many of these defects disappeared. Mantles made from this fibre do not shrink continuously, nor to any considerable extent, so that crumpling does not occur; the decrease in light-giving power is very much less than with the cotton mantles, the life is much longer, and the resistance to shock very much greater. Microscopic examination of the fibres, and of the ash left after burning off, shows that these differences are traceable to differences in the mechanical structure of the two fabrics. The cotton thread is spun from a very large number of very short fibres, which are twisted together, whereas the separate fibres of ramie are of much greater length, and the torsion in the thread correspondingly less. In the case of artificial silk, continuous filaments are spun into threads, and this simple fact accounts for the very much greater durability and elasticity of mantles made from this fabric. The introduction of ramie for the manufacture of mantles effected no great alterations in the processes employed in the case of cotton; the treatment of artificial silk, however, requires a profoundly modified method, and in consequence the preparation of this fabric and the manufacture of mantles from it, are considered separately in another chapter. Though the manufacture of artificial silk was first commenced in France, it is in Germany that its adaptation to the incandescent mantle industry has been successfully effected. Its adoption, however, has not yet become general, and by far the greatest number of mantles are to-day made from ramie. In the United States, where the early working of the monazite deposits gave a great impetus to the industry, the manufacturers still cling largely to the older methods, so that even now quite a considerable number of mantles are made from cotton. In the present chapter, a short account will be given of the methods employed in the manufacture of mantles from ramie and cotton. The general methods of preparation of cotton fabrics are well known. Ramie is prepared from the tschuma plant, which is found in India, China, and other parts of Asia. The fibre is obtained from the inner side of the bark; this is dried, pressed into bales, and exported. After removal of gum and resin, by heating with sodium hydroxide solution under pressure, the fibre is bleached, dried and cleaned, and then combed and spun in the usual manner.[517] [517] For the preparation and technical uses of Ramie, or Rhea, as it was formerly called, _vide_ Cross, ‘The Industrial Uses of Cellulose,’ in the _Cantor Lectures of the Society of Arts_, 1897, ~vi~, p. 20.