221), or by agitators acting on the principle of pumps, and raising the liquor and sludge from the bottom. Such agitators have been patented in Germany, but had been in use much earlier in the Author’s tanyard. An agitator on the principle of the screw-propeller of a steamship, placed near the bottom of the pit, and protected by a lattice, may also be usefully employed (Fig. 26). Skins are frequently limed in paddles, or stirred up by blowing air into the pit. The latter method is neither effective nor economical in power. [Illustration: FIG. 26.--Suspension Lime-Pit.] As has been noted, the solubility of lime, and consequently the strength of the lime-liquor, is diminished by rise of temperature, but its solvent action on hide-substance is much increased. As a consequence, the loosening of the hair proceeds much more rapidly in warm limes, but the hides do not plump well, and become loose, hollow and inclined to “pipe” in the grain, and to weigh out badly, and for sole leather the method is therefore in every way disastrous. In the few cases among the lighter leathers where a decided softening and loosening of the texture of the skin is required, it is possible that useful advantage may be taken of this effect; but it would be exceedingly difficult to regulate the temperature of an ordinary lime-pit with accuracy, and better results could probably be obtained with suspenders in which the liquor could be constantly circulated. When limes are very cold, in spite of the greater strength of solution, the action is very much checked, and where goods are frozen into pits in severe weather, there is but little danger of overliming, although the usual time may be much exceeded. It is generally best to work limes at about the ordinary summer temperature, and this is better done in winter by warming the limeyard than by any direct heating of the limes. If lime which has cooled after slaking is used, the water with which limes are made may safely be warmed in midwinter to a temperature not exceeding 20° C. The quantity of lime used by different tanners, and for different sorts of hides and skins, is very variable, not only according to the effect which it is desired to produce, and the way in which it is used, but from the arbitrary fancy of the user, since its limited solubility renders an excess comparatively innocuous. For sole-leather, the amount recommended varies from under 1 per cent. to 10 or 12 per cent. on the green weight of the hide; but probably 2-3 per cent. is all that can be really utilised, the remainder being wasted. In order, however, to utilise the whole of the lime, very frequent handling or agitation is required to ensure its uniform distribution. It must also be borne in mind that the strength of commercial limes varies from above 80 down to 30 per cent. of available calcium oxide.