The work of liquefying the gases had been taken up by Faraday during his hours of liberty from other duties. It was probably his characteristic dislike to “doubtful knowledge” which prompted him to re-examine a substance which had at one time been regarded as chlorine in a solid state, but which Davy in 1810 had demonstrated to be a hydrate of that element. The first work was, as narrated above, to make a new analysis of the supposed substance. This analysis, duly written out, was submitted to Sir Humphry, who, without stating precisely what results he anticipated might follow, suggested heating the hydrate under pressure in a hermetically sealed glass tube. This Faraday did. When so heated, the tube filled with a yellow atmosphere, and on cooling was found to contain two liquids, one limpid and colourless like water, the other of an oily appearance. Concerning this research a curious story is told in the life of Davy. Dr. Paris, Davy’s friend and biographer, happened to visit the laboratory while Faraday was at work on these tubes. Seeing the oily liquid, he ventured to rally the young assistant upon his carelessness in employing greasy tubes. Later in the day, Faraday, on filing off the end of the tube, was startled by finding the contents suddenly to explode; the oily matter completely disappearing. He speedily ascertained the cause. The gas, liberated from combination with water by heat, had under the pressure of its own evolution liquefied itself, only to re-expand with violence when the tube was opened. Early the next day Dr. Paris received the following laconic note:-- DEAR SIR,-- The _oil_ you noticed yesterday turns out to be liquid chlorine. Yours faithfully, M. FARADAY. Later he adopted a compressing syringe to condense the gas, and again succeeded in liquefying it. Davy, who added a characteristic note to Faraday’s published paper, immediately applied the same method of liquefaction by its own pressure to hydrochloric acid gas; and Faraday reduced a number of other gases by the same means. These researches were not without danger. In the preliminary experiments an explosion of one of the tubes drove thirteen fragments of glass into Faraday’s eye. At the end of the year he drew up a historical statement on the liquefaction of gases, which was published in the _Quarterly Journal_ for January, 1824. A further statement by him was published in the _Philosophical Magazine_ for 1836; and in 1844 his further researches on the liquefaction of gases were published in the _Philosophical Transactions_.