I would here remark that I changed the process from liming to sweating in the sole leather in 1836—the only change I have made in tanning for twenty years; and for sole leather, it has been proved to be quite as good as liming, if not better, and somewhat cheaper; besides yielding a greater gain of weight, and when well tanned, making leather more impervious to water. Liming and “bating,” however, for light leather, is preferable. Salted hides do not require more than two-thirds the time to soak; but generally rather longer to sweat. After the hides are prepared for tanning, the next process is what is commonly called “handling,” which should be performed two or three times a day in a weak “ooze” until the grain is colored. New liquors, or a mixture of new and old, are preferable for Spanish or dry hides—old liquors for slaughter. They are then, after a fortnight, laid away in bark, and changed once in two or four weeks, until tanned. Much care and judgment are necessary in proportioning the continually increasing strength of the liquors to the requirements of the leather in the different stages of this process. The liquors should be kept as cool as possible, within certain limits, but ought never to exceed a temperature of eighty degrees; in fact, a much lower temperature is the maximum point, if the liquor is very strong; too high a heat, with a liquor too strongly charged with the tanning principle, being invariably injurious to the life and color of the leather. From this it would seem that time is an essential element in the process of tanning, and that we cannot make up for the want of it by increasing the strength of the liquor, or raising the temperature at which the process is conducted, any more than we can fatten an ox or horse by giving him more than he can eat. Hides that are treated with liquor below the proper strength become much relaxed in their texture, and lose a portion of their gelatine. The leather necessarily loses in weight and compactness, and is much more porous and pervious to water. The warmer these weak solutions are applied, the greater this loss of gelatine. To ascertain whether a portion of weak liquor contains any gelatine in solution, it is only necessary to strain a little of it in a glass, and then add a small quantity of a stronger liquor. The excess of tannin in the strong, seizing upon the dissolved gelatine in the weak liquor, will combine with it, and be precipitated in flakes, of a dark, curdled appearance, to the bottom. At the Prattsville Tannery, the greatest strength of liquor used for “handling,” as indicated by Pike’s _bark-ometer_, (an instrument to test only FRESHLY made liquors,) is sixteen degrees; of that employed in laying away, the greatest strength varies from thirty-five to forty-five degrees.