This same web of association extends just as clearly to the most important work which has been done at the Royal Institution in the present generation, and which is still being prosecuted there--the work, namely, of Professor James Dewar on the properties of matter at excessively low temperatures. Indeed, this work is in the clearest sense a direct continuation of researches which Davy and Faraday inaugurated in 1823 and which Faraday continued in 1844. In the former year Faraday, acting on a suggestion of Davy's, performed an experiment which resulted in the production of a "clear yellow oil" which was presently proved to be liquid chlorine. Now chlorine, in its pure state, had previously been known (except in a forgotten experiment of Northmore's) only as a gas. Its transmutation into liquid form was therefore regarded as a very startling phenomenon. But the clew thus gained, other gases were subjected to similar conditions by Davy, and particularly by Faraday, with the result that several of them, including sulphurous, carbonic, and hydrochloric acids were liquefied. The method employed, stated in familiar terms, was the application of cold and of pressure. The results went far towards justifying an extraordinary prediction made by that extraordinary man, John Dalton, as long ago as 1801, to the effect that by sufficient cooling and compressing all gases might be transformed into liquids--a conclusion to which Dalton had vaulted, with the sureness of supreme genius, from his famous studies of the properties of aqueous vapor. Between Dalton's theoretical conclusion, however, and experimental demonstration there was a tremendous gap, which the means at the disposal of the scientific world in 1823 did not enable Davy and Faraday more than partially to bridge. A long list of gases, including the familiar oxygen, hydrogen, and nitrogen, resisted all their efforts utterly--notwithstanding the facility with which hydrogen and oxygen are liquefied when combined in the form of water-vapor, and the relative ease with which nitrogen and hydrogen, combined to form ammonia, could also be liquefied. Davy and Faraday were well satisfied of the truth of Dalton's proposition, but they saw the futility of further efforts to put it into effect until new means of producing, on the one hand, greater pressures, and, on the other, more extreme degrees of cold, should be practically available. So the experiments of 1823 were abandoned.