and the hide would fall, at any rate when the lime was completely carbonated, while hides would remain plumpest in waters most free from substances capable of neutralising lime. From this we may conclude, what may be _a priori_ expected, that the purer the water, the plumper limed hides remain in it. In soft but peaty waters, hides fall rapidly, from the neutralisation of the lime by the weak organic acids of the peat. Such waters are dangerous for domestic use from their solvent action on lead, but this danger can be entirely removed by storing the water in limestone reservoirs, or allowing it to flow slowly through a limestone culvert before use. In some towns in the north of England a small quantity of lime is added so as to neutralise the water as it leaves the reservoir and before it enters the mains. Wherever the conditions of putrefaction or decaying organic matter are present, as in a bate, hides fall rapidly, and in extreme cases even the presence of the stronger acids will not maintain plumpness. Eitner mentions the case of a stream at Vissoko in Bosnia, which was in special repute among the tanners from its power of pulling down hides rapidly, and which took its rise in a common on which the pigs of the town were pastured. The causes of this action are no doubt due to the products of putrefaction, but are somewhat obscure. Bacteria present in water are a frequent source of injury in the soaks, and probably in other stages of the tanning process. Rain water and the water of streams in mountain districts of hard igneous rock are generally nearly free from mineral constituents. This is the case with the Glasgow water from Loch Katrine, and the Thirlmere water which supplies Manchester. Such water, if cold enough, and free from mud and organic impurity, is the best for almost every purpose in the tannery. Most river-water contains material quantities of mineral matter, though it is usually softer than that of springs or wells. For further details as to the chemical examination of water, and the methods of determining the amounts of its different constituents, see L.I.L.B., pp. 18 _et seq._ CHAPTER XI. _SOAKING AND SOFTENING OF HIDES AND SKINS._ As has been explained in the last chapter, hides and skins come into the hands of the tanner either uncured (“green”), as they are taken off the animal, preserved with salt or some other antiseptic, dried, or “drysalted” in which both methods are combined. His object in each case is to remove blood and dirt, and to restore the hide to its soft and natural condition; but the treatment required varies much with the state of the hides.