This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
In a lecture lately delivered on "New Applications of the Mechanical Properties of Cork to the Arts," the lecturer demonstrated experimentally that in solid substances no appreciable change of volume resulted from change of pressure; even India rubber was shown to be extremely rigid. Cork, however, appeared to be a solitary exception to this law, being eminently capable of cubical compression, both from forces applied in opposite directions, and from pressure from all sides, such as arose when the substance was immersed in water and subjected to hydraulic pressure. The cause of this anomalous and valuable property of cork was then investigated, and it was shown to arise from its peculiar structure, which rendered it, in many respects, more like a gas than a solid. Cork was composed exclusively of minute closed cells, the walls of which were readily permeated by gases, but were impervious to liquids. The cells were filled with air, which, when pressure was applied, yielded readily and expanded again when the pressure was removed. The impermeability of the cells to liquids prevented cork from getting water-logged when exposed to such fluids in bottles. This property, combined with permeability to gases, rendered cork superior to India rubber for many purposes, because it permitted transpiration while excluding the moisture.
There was lately a trial made to substitute cottonwood for corkwood, but with unsatisfactory results.