Anderson, Ure, Chevruel, Fownes, Watts, Brisbane, men of science; to these we are indebted for the little that is known of corkwood, and although perhaps much more could be said by elaboration, it will suffice to record the facts in this monograph for the purpose involved. But to the data assembled may be added much in commentation, for the material becomes more interesting the more it is studied, and most naturally excites comparison with other materials and substitutes, as well as calling forth a discussion as to the dangers involved by its presence in the places where, by skill of hand and machinery, it is transformed into the many commercial forms, noted in this article. We comment upon its growth, which is truly wonderful and all-absorbing in its many interesting phases; it takes us to the romance of the East and the enchantment of the Moorish occupation; through which these forests of cork-producing trees passed and yet remain to furnish the present generation. We comment upon its lightness and buoyancy, due to the presence of air and excess of hydrogen, known to be lighter than air; and the small percentage of other matter which, being of less importance, make its other quality so renowned as to make it the most wonderful growth of its kind. Its imperviousness to water and other liquids have given us moments of reflection, upon this phenomenon, but now known to be because of the cellulose composing the cell walls and which, when the substance is under compression, practically is all that remains, except for the small quantity of resin, etc., to resist the passage of liquids or gases. But heretofore when these commentations have reached the burning point, its physical nature was entirely eliminated from the conjecturing and the important part neglected, that as the cork contained fifty-three per cent of air, heat of 450 degrees expands to the point of explosion, the contents of those cells nearest the surface, which giving up their oxygen feed the flames and in their passage help to disintegrate the cell walls and make them more easily ignited. Thus causing a rapid burning, flash fire which, in its fury, Pluto could not rival, only racing over the surface of the cork, burning but slightly, yet helped by other conditions, resulting in a fire destructive and fierce. This rapid burning leaves the outer surface of the cork charred and flaky and causes a discoloration beneath it attributed to the dissolving of the resins, etc. Of course where there is a large quantity of corkwood the extent of the burning must necessarily be greater and the depth of the char increased. But it appears that the first flash burning produces a sort of protection coat of carbon around the remaining unburned portions which a subsequent flame penetrates with difficulty.[28] [28] In the making of insulation material, the carbonization of the cork is accomplished without destruction of fibre and stands a high flame test.