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 caloric, be susceptible of combination with Sulphur, phosphorus, and the metals. There is nothing that we know of, which, a priori, should render these combinations impossible; for combustible bodies being in general susceptible of combination with each other, there is no evident reason for hydrogen being an exception to the rule: However, no direct experiment as yet establishes either the possibility or impossibility of this union. Iron and zinc are the most likely, of all metals, for entering into combination with hydrogen: but, as these have the property of decomposing water, and as it is very difficult to determine whether the small portions of hydrogen gas, obtained in certain experiments with these metals, were previously combined with the metal in the state of solid hydrogen, or if they were produced by decomposition of a minute quantity of water. The more care we take to prevent the presence of water in these experiments, the less is the quantity of hydrogen gas procured; and, when very accurate precautions are employed, even that quantity becomes hardly sensible.

However this inquiry may turn out respecting the power of combustible bodies, as sulphur, phosphours, and metals, to absorb hydrogen, we are certain that they only absorb a very small por-