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The Story of Coal-Gas 69 favour. The brilliancy of the light for a reduced consumption of gas was incontestable, but the neces- sity to replace the mantles frequently were held to outweigh any advantages accruing from their use. Incandescent gas-lighting, however, had received too pronounced an impetus to permit another retire- ment into oblivion. Other scientists attacked the issue, and they succeeded where the original inventor failed, although the latter, by continuing his work, overcame the disadvantages one by one. It was feared that the cost of the mantles would always remain a. prohibitive factor against universal use, seeing that thoria, is obtained fi om a. particular sand, known as “ monazite,” the deposits of which are somewhat scanty, the richest being found upon the coast of Brazil. But the increased demand for the commodity led to improved and cheaper methods for its extraction, with the result that the price of the mantles was steadily reduced. It was the base which constituted the greatest weakness of the mantle, and various substitutes for cotton were tried. First ramie met with conspicuous favour, inasmuch as it was found to be superior to the cotton. Then another chemist indicated that artificial silk was superior to both cotton and ramie. Another investigator, Plaisetty, found that knitted artificial fibre was better still, and that ammonia was superior to collodion for hardening the mantle. This inventor met with the greatest measuie of success, and his original idea, modified and improved with the passage of time, holds the world to-day. As is well known, the first Welsbach mantle was of the upright type, resembling an attenuated trun-