. The Annual of scientific discovery: or, Year-book of facts in science and art. Industrial arts -- Yearbooks; Science -- Yearbooks. MECHANICS AND USEFUL ARTS. 63 speculations throw considerable doubt on the accuracy of the above formula when applied to steam and other condensable vapors. Several years ago, Dr. Joule and Professor William Thomson announced, as the result of applying the new dynamical theory of heat to the law of Carnot, that, for tempera- tures above two hundred and twelve degrees Fahrenheit, there is a very con- siderable deviation from the gaseous laws in the case of steam.
. The Annual of scientific discovery: or, Year-book of facts in science and art. Industrial arts -- Yearbooks; Science -- Yearbooks. MECHANICS AND USEFUL ARTS. 63 speculations throw considerable doubt on the accuracy of the above formula when applied to steam and other condensable vapors. Several years ago, Dr. Joule and Professor William Thomson announced, as the result of applying the new dynamical theory of heat to the law of Carnot, that, for tempera- tures above two hundred and twelve degrees Fahrenheit, there is a very con- siderable deviation from the gaseous laws in the case of steam. Later, in 18-55, Professor Maquorn Rankine has given a new theoretical formula for the density of steam, independent of Gay-Lussac's law, and confirmatory of Professor Thomson's surmise. But as yet these speculations need the evi- dence and verification of direct experiment. The density of steam is ascertained by vaporizing a known weight of water in a glass globe of known capacity, and noting the exact temperature at which the whole of the water becomes converted into steam. From these three elements — volume, weight, and temperature — the specific gravity is known. But in pursuing this method, these two difficulties must be over- come : First, the pressure of the steam renders it necessary that the glass globe should be heated in a strong, and consequently opaque, vessel; second, as steam rapidly expands in volume for any increase of temperature, beyond the temperature of saturation, it would, in any case, be impossible to decide by the eye the temperature at which the whole of the water became vapor- ized. The temperature of saturation, or temperature at which the whole of the moisture is converted into steam, while no part of the steam is super- heated, must be determined with the utmost accuracy, or the results are of no value. The difficulties thus resolve themselves into finding some other test of suf- ficient accuracy and delicacy to determine the point of saturatio
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