Such are some of the strictly scientific results of the low-temperature work. But there are other results of a more directly practical kind--neither more important nor more interesting on that account, to be sure, but more directly appealing to the generality of the non-scientific public. Of these applications, the most patent and the first to be made available was the one forecast by Davy from the very first--namely, the use of liquefied gases in the refrigeration of foods. Long before the more resistant gases had been liquefied, the more manageable ones, such as ammonia and sulphurous acid, had been utilized on a commercial scale for refrigerating purposes. To-day every brewery and every large cold-storage warehouse is supplied with such a refrigerator plant, the temperature being thus regulated as is not otherwise practicable. Many large halls are cooled in a similar manner, and thus made comfortable in the summer. Ships carrying perishables have the safety of their cargoes insured by a refrigerator plant. In all large cities there are ice manufactories using the same method, and of late even relatively small establishments, hotels, and apartment houses have their ice-machine. It seems probable that before long all such buildings and many private dwellings will be provided with a cooling apparatus as regularly as they are now equipped with a heating apparatus. The exact details of the various refrigerator machines of course vary, but all of them utilize the principles that the laboratory workers first established. Indeed, the entire refrigerator industry, now assuming significant proportions, may be said to be a direct outgrowth of that technical work which Davy and Faraday inaugurated and prosecuted at the Royal Institution--a result which would have been most gratifying to the founder of the institution could he have forecast it. The usual means of distributing the cooling fluids in the commercial plants is by the familiar iron pipes, not dissimilar in appearance (when not in operation) to the familiar gas, water, and steam pipes. When operating, however, the pipes themselves are soon hidden from view by the thick coating of frost which forms over them. In a moist beer-cellar this coating is often several inches in thickness, giving a very characteristic and unmistakable appearance.