But it is under the third point of view that the preservative process is more important and interesting, inasmuch as it admits of a far more extensive application. We speak of the abstraction of _air_. Atmospheric air affects dead organic matter chiefly through the agency of the oxygen which forms one of its constituents; and it is principally to insure the expulsion of oxygen that air is excluded. The examples which illustrate the resulting effects are numerous and varied. Eggs have been varnished so as to exclude air, and have retained the vital principle in the chick for years; and it is a familiar domestic practice, to butter the outside of eggs as a means of keeping them. The canisters of preserved provisions, however, are the most direct and valuable result of the antiseptic action by exclusion of air. The Exhibition Jury on Class 3, in their Report on this subject, speak thus warmly thereupon:--'It is impossible to overestimate the importance of these preparations. The invention of the process by which animal and vegetable food is preserved in a fresh and sweet state for an indefinite period, has only been applied practically during the last twenty-five years, and is intimately connected with the annals of arctic discovery. The active measures taken to discover a north-west passage, and to prosecute scientific research, in all but inaccessible regions, first created a demand for this sort of food; and the Admiralty stimulated the manufacturers to great perfection in the art. As soon as the value of these preparations in cold climates became generally admitted, their use was extended to hot ones, and for the sick on board ship under all circumstances. Hitherto they had been employed only as a substitute for salt beef or pork at sea, and if eaten on shore, it was at first as a curiosity merely. Their utility in hot climates, however, speedily became evident; especially in India, where European families are scattered, and where, consequently, on the slaughter of a large animal, more is wasted than can be consumed by a family of the ordinary number.' Whatever improvements may have been introduced by later manufacturers, the principle involved in the meat-preserving processes is nearly as M. Appert established it forty years ago. His plan consisted in removing the bones from the meat; boiling it to nearly as great a degree as if intended for immediate consumption; putting it into jars; filling up the jars completely with a broth or jelly prepared from portions of the same meat; corking the jars closely; incasing the corks with a luting formed of quicksilver and cheese; placing the corked jars in a boiler of cold water; boiling the water and its contents for an hour; and then allowing the cooling process to supervene very gradually.