1. Oak bark and valonia, or valonia extract. 2. Oak bark, valonia, and gambier. 3. Oak bark, quebracho extract, and myrobalan extract. 4. Chestnut, quebracho and valonia extracts. 5. Chestnut and oakwood extracts. 6. Oakwood and quebracho extracts, and divi-divi or algarobilla. 7. Quebracho extract, myrobalans, and valonia. 8. Quebracho, mangrove, and valonia extracts. 9. Oakwood, mimosa, and valonia extracts. 10. Hemlock and oak extracts (American union tannage). _For Dressing Leathers._ 1. Oak bark and sumach. 2. Oakwood and quebracho extracts, and sumach. 3. Synthetic tannin and oakwood extract. 4. Synthetic tannin and myrobalans. 5. Gambier and sumach. 6. Wattle bark and myrobalans. Sumach is often used alone for some classes of goat, sheep, and calf skins. Synthetic tannins can also be used alone for light leathers. Many other variations may be tabulated, for nearly every tanner has his own recipe, having found by experience the blend of tannage that best suits his trade. Apart from these innumerable combinations, the only method whereby the vegetable tanning process may be hastened is the mechanical, for which purpose either the paddle (Fig. 25) or the drum (Fig. 13) is used. The former consists of a wheel constructed of wooden shelves which, when in motion, dip a little way into the tan liquor in a vat, and so keep it in constant circulation. The drum is fitted inside with wooden shelves or pegs, which carry some of the hides or skins to the top of the drum at each revolution. Were it not for these shelves, the tannage would probably be irregular or otherwise unsatisfactory, as the hides would always be heaped together at the bottom of the drum. The paddles and drum are more often used for light than for heavy leather, as they not only have the effect of making the leather loose on the grain, but also make it soft and supple, characteristics which are not required in most of the heavy leathers. [Illustration: FIG. 25 PADDLE VAT]