It was with regard to gases, however, that Faraday's most striking chemical work was done. He succeeded in liquefying several gases, and was the first to make clear that all matter could probably exist in each of the three different states--solid, liquid and gaseous--according as the proper conditions for each particular state were present. One might almost have expected that the serious dangers incurred in his early days in the Royal Institution, when his chief, Sir Humphry Davy, suffered so severely and he himself was more than once involved, might have deterred him from further investigation along similar lines; but Faraday's ardor for scientific investigation overcame any hesitancy there might have been. The effect of gases upon human beings proved as attractive to Faraday as it had been to Davy. His experiments upon chlorine threatened to prove seriously injurious to his throat, and he was warned of the danger that he was running in the effort to determine whether such gases were respirable and what their effects upon human beings were. The warning was disregarded, however, though he exercised somewhat more care in subsequent observations. His experiments in the respiration of gases finally led him to a discovery of cardinal importance in the very practical field of anæsthesia. Sir Humphry Davy, just at the beginning of the nineteenth century, had made a series of interesting experiments on nitrous oxide gas, the so-called "laughing gas," and had pointed out very definitely its anæsthetic properties. While suffering from toothache he had inhaled the gas, and had experienced prompt alleviation of the pain. He described in detail these curious effects, and suggested that there might be a place for nitrous oxide in surgery, at least for minor operations. The words he employed with regard to this subject show that the idea of anæsthesia, as we now understand it, had come to him very definitely. Not quite a score of years later, Faraday, recalling the experiments of Davy with nitrous oxide, studied sulphuric ether, and showed that the inhalation of the vapor of this substance produced anæsthetic effects very similar to those of nitrous oxide gas, but with the possibility of prolonging them much more easily and apparently with less danger than would be the case with the latter. In every history of anæsthesia, these two sets of experiments at the Royal Institution must be set down as foundation-stones, and Faraday's name particularly must be hailed as one of the initiators of a supremely beneficent advance in modern surgery.