Page:A Practical Treatise on Brewing (4th ed.).djvu/242

226 thunder-storm, and its immediate recommencement when the wort was pumped out of the vat embedded in the earth, into casks placed on wooden stands, affords a strong proof of the power of electricity over these processes. We cannot doubt but the cessation of the process was in this instance the effect of the negatively electric state of the earth which is generally observed before thunder. Whether the isolation produced by transferring the liquor from the vat into casks supported by wooden stands, was anywise effective in its recommencement, we cannot say. Negative surfaces do not appear to promote the chemical changes to which such liquors are disposed, at least we think this a fair inference from the results of the following experiments.

Into three pots of similar size and shape, two of them made of copper, and one of wood, we put equal quantities of wort. We kept them precisely in the same circumstances; but one of the copper pots was rendered negative by having a disk of zinc in its bottom. In the course of three weeks the worts in the other two pots underwent spontaneous fermentation, became sour, and ultimately putrid, whereas that in the negative pot, continued free from every appearance of fermentation and chemical change, and as sweet to the taste for months as it was at the beginning. These