Before the invention of Sir Humphrey Davy's Safety Lamp, this property of the gas gave rise to a variety of contrivances for affording the miners sufficient light to pursue their operations; and one of the most useful of these inventions was a mill for producing light by sparks elicited by the collision of flint and steel. Such a stream of sparks may appear a very crude and unsatisfactory solution as judged by present standards, but it was at least an ingenious application of the facilities available at that time. Various other devices were resorted to in the coal-mines before the introduction of a safety lamp. In discussing the candle it is necessary again to go back to an early period, for it slowly evolved in the course of many centuries. It is the natural descendant of the rushlight, the grease-lamp, and various primitive devices. Until the advent of the more scientific age of artificial lighting, the candle stood preeminent among early light-sources. It did not emit appreciable smoke or odor and it was conveniently portable and less fragile than the oil-lamp. Candles have been used throughout the Christian era and some authorities are inclined to attribute their origin to the Phoenicians. It is known that the Romans used them, especially the wax-candles, in religious ceremonies. The Phoenicians introduced them into Byzantium, but they disappeared under the Turkish rule and did not come into use again until the twelfth century. The wax-candle was very much more expensive than the tallow-candle until the fifteenth century, when its relative cost was somewhat reduced, bringing it within the means of a greater proportion of the people. Nevertheless it has long been used, chiefly by the wealthy; the departing guest of the early Victorian inn would be likely to find an item on his bill such as this: "For a gentleman who called himself a gentleman, wax-lights, 5/." Poor men used tallow dips or went to bed in the dark. It is interesting to note the importance of the candle in the household budget of early times in various sayings. For example, "The game is not worth the candle," implies that the cost of candle-light was not ignored. In these days little attention is given to the cost of artificial light under similar conditions. If a person "burns a candle at both ends" he is wasteful and oblivious to the consequences of extravagance whether in material goods or in human energy.