All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

68 All About Inventions best results were obtained by combining thoria and ceria, and he patiently pursued his tests until he discovered the most satisfactory proportion of the two substances. Simultaneously he set about discovering the most serviceable form for the mantle, and found that a knitted hose-like foundation of cotton fabric gave the best results. This was soaked in what was known as the lighting fluid, which to-day comprises thoria 99 per cent, and ceria i per cent. The proportion of ceria is thus very slender, amounting in a single mantle to a. few microscopic grains. But it is the ceria which gives the lighting brilliancy, the thoria giving the fragile skeleton its strength. When the cotton is burned away the rare earths, in the form of metallic oxide ash, are left clinging together, and the mantle retains its original form, which is maintained so long as no extraneous force is applied, such as a draught of air, a jar, or excessive vibration. But even in its pre-burnt form the mantle was conspicuously fragile, since the woven material form- ing the base is thin, light, and delicate. To render the discovery of commercial value the mantles had to be given sufficient strength to withstand the rigors of transport in safety, and this end was accomplished partially by dipping the mantle in a collodion solution. While the appearance of this incandescent mantle was hailed with enthusiasm by gas-lighting enthu- siasts, it was not strikingly successful. The mantles were far too fragile, and their relatively short life in the average home, combined with their expense, caused the invention to meet with pronounced dis-