A peculiarity of the valonia is that it often strikes out a sort of sugar sweat, which gives the cup a less attractive appearance, but denotes the presence of large quantities of tannin. Valonia is used almost wholly for sole leather, either alone or in combination with pine or oak bark or knoppern and myrabolams. The union of valonia and knoppern is that in most general use. Valonia gives the leather a yellowish appearance, as it deposits a great deal of yellow bloom. The leather is very firm and of good wearing qualities. The weight results are also excellent, as will be seen below. To sole leather there are usually given from one to three layers of valonia. The demand for valonia is increasing more and more every year, and the present outlook does not indicate any relaxation of its popularity. Its use for upper leather is very limited. Myrabolams are mainly used in England and Austria, and give a nice light-colored leather, both upper and sole, although rarely used alone. Their main use is for dyeing purposes. They are indigenous to the East Indies. Sumac is so well known that treating of it is superfluous. Its use is very extensive, and it is a general favorite for light, fine leather, which is mostly used for colors. _Gambier_--Is in general use in England and to some extent in Germany. _Catechu_.--Obtained from India, resembles gambier greatly. Its use is almost wholly confined to England. It is also consumed by the silk manufacturers in preference to gambier, for weighting purposes. PATHOLOGICAL. We now leave the physiological class and take up those tanning materials included in the pathological class, or those of abnormal growth. _Galls_.--These are not consumed to any great extent at the present period, but formerly they were used quite extensively. The galls are found upon the leaves of the oak or sumac, etc. The direct cause of their growth is that a certain wasp (cynips galles) stings into the leaf and after depositing its egg, flies away. The egg develops into a larva and then into a full-fledged wasp, boring its way out of the gall which has served as a protection and nourisher. This accounts for the hole noticed in almost every gall. The different varieties include Aleppo. It is found upon the same trees as the valonia and contains 60 to 75 per cent. tannin; Istrian galls, 32 per cent. tannin; Persian, 28 to 29 per cent. tannin. Chinese galls, giving 80 to 82 per cent. tannin, are the results of the sting of a louse, and make a very light-colored leather. The dyers also use this material for coloring.