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Oil-lamp clocks are clocks consisting of a graduated glass reservoir to hold oil - usually whale oil, which burned cleanly and evenly - supplying the fuel for a built-in lamp. As the level in the reservoir dropped, it provided a rough measure of the passage of time. The principle behind such a time-keeping device is that it measure a quantity that either decreases or increases at a constant rate. Lamps or candles, burning fuel at a steady pace, fit this category, and as a bonus produce useful light. Hourglasses depend on the steady draining of fine sand through a small aperture. Water clocks or clepsydra measure a gain or loss of water by using drops of uniform size and frequency. The Persian fenjaan made use of the constant time it took for the sinking of a floating bowl with a hole in its underside. History it is unknown when, where or in which way the oil-lamp clocks were first introduced. this clock was but mainly used in the 18th century. The Oil-Lamp clocks were not of much use due to which they got eliminated in the mid-18th centuries. ==Related articles== *Candle clock *Water clock *Hourglass 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Oil-lamp clock」の詳細全文を読む スポンサード リンク
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