Coal; its history and uses . when their temperatureshad ceased to fall they were once more determined, theywould be found to be again the same. It would howeverbe observed that the water would take longer to cool thanthe oil, and if by chance the vessels had been placed upona block of ice, that containing the water would havemelted the larger hole in the ice. These circumstanceswould lead to the suspicion (which closer investigationswould confirm) that the water had lost the larger quantityof heat, though each liquid had been cooled through thesame number of degrees of temperature. The followi
Coal; its history and uses . when their temperatureshad ceased to fall they were once more determined, theywould be found to be again the same. It would howeverbe observed that the water would take longer to cool thanthe oil, and if by chance the vessels had been placed upona block of ice, that containing the water would havemelted the larger hole in the ice. These circumstanceswould lead to the suspicion (which closer investigationswould confirm) that the water had lost the larger quantityof heat, though each liquid had been cooled through thesame number of degrees of temperature. The following is 236 COAL. CHAP. Tii. an experiment by means of which the fact that equalweights of different substances, when cooled through thesame range of temperature, do not give out equal quan-tities of heat, may be rendered evident to a largenumber of persons at once. A small glass cell containing some water and a ther-mometer is placed in front of a lime-light lantern, and bymeans of a lens an enlarged image of the cell and its. Fig. 49.—Lantern Calorimeter. contents is formed upon a screen. The thermometer is soconstructed that the whole of it may be visible. The stemis bent round parallel to the bulb, it is graduated for 20only, from 60° to 80° F., and the graduations are engravedupon a piece of glass to which the instrument is attached,and by means of which it is supported. A large glasstrough filled with water is placed between the cell and thelantern. This allows the light to pass through, but cutsoff so much of the heat that the thermometer remainsstationary though exposed to the full blaze of the lime-light. Previous to the performance of the experiment thetemperature of the water in the cell must be adjusted to alittle over 60° T. (say 60^°), and equal weights of water andquicksilver contained in two separate tubes must be heatedby immersion in a vessel of boiling water. If the tube inwhich the water is placed be graduated, any loss which CHAP. vit. COAL AS A SOURCE
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherlo, booksubjectcoal
