Page:A Treatise on the Culture of the Vine and, and the Art of Making Wine.pdf/191

 full of water, inverted on the shelf of the pneumatic-trough, at the temperature of 54° to 50°, the first phenomena of fermentation in a few minutes appear. The empty part of the flank is soon filled with bubbles and scum, and mach carbonic acid passes into the bell; and these movements do not cease till the liquor has become vinous. In no case has it been observed, that there was an absorption of atmospheric air.

If, instead of allowing a free issue to the garous matters which escape during fermentation their disengagement is opposed by conducting it in close vessels, then the fermentation slackens, and with difficulty, and, after a long time, it terminates its periods.

It appeared, from these facts, that the atmosspheric air is not necessary to fermentation, since it took place in close vessels; but it was important to ascertain, whether the air bubbles dispersed through the fermentable fluid, or the couch of air above it might not contribute to this operation.

To ascertain this, M. Guy Lossac instituted an experiment, which has thrown the greatest light on the question. He introduced some very ripe grapes under an eprouvette of quicksilver, and, to drive away the small air bubbles adhering to the walls, he filled it successively, and at many relays, with carbonic acid and mercury. He then crushed