Skins which are much damaged on the grain, or otherwise faulty, are smoothed with lump pumice on the flesh-side, either by hand or machine. They are then dyed on this side, mostly by dipping, but occasionally with the brush, in which case, the method described is slightly modified. Indebtedness is acknowledged to F. Kathreiner, of Worms, and David Richardson, of Newcastle, for much information on the production of light leathers. The Plates 1 to 8 represent the works of Messrs. Tréfousse et Cie., at Chaumont (Haute-Marne). CHAPTER XXII. CONSTRUCTION AND MAINTENANCE OF TANNERIES. As few architects have specially studied the construction of tanneries, and in most cases much of the arrangement depends on the knowledge of the tanner himself, a short chapter on the subject will not be out of place. In the selection of a site, a clay or loamy soil is to be preferred to a gravelly or sandy one, as lessening the liability to leakage, and waste of liquor. Perhaps, however, the first consideration of all is the water supply, since for manufacturing purposes town water is generally very expensive. With regard to quality and impurities of water, information may be found on p. 83; but, as a general rule, the softer and purer the supply the better. It is also of great advantage when the source is at such a level as to flow into the tan-yard, or at least into the beam-house, without pumping. Filtration too, when needed, is much facilitated by a sufficient head of water. Of scarcely less importance than the water supply is the drainage of the yard. It not unfrequently happens that tanneries are prohibited from discharging their refuse liquors, limes, and soaks into rivers and watercourses, and it is sometimes a matter of extreme difficulty to find any other way of getting rid of them. In default of an outlet, recourse must be had to precipitation and filtration, but this is a costly expedient, and in fixing a site for a new yard it is far better to provide against such a possible contingency. Should, however, such means become necessary, it may be borne in mind that limes and liquors in great measure mutually precipitate each other, and that if all the various refuse is run into one tank, mixed, and settled, much is accomplished in the direction of purification. The further treatment of the effluent water must be determined by its nature and composition.