294 NOTES ON TANNINE SUBSTANCES. 



possible we may get it from Algeria, the cork tree growing there very fine. 

 The bark is usually dried in the sun ; but if it should become wetted 

 when drying, the operation is finished by means of artificial heat. 



The kiln-dried may be distinguished by being of a somewhat browner 

 hue than the reddish tint of the sun-dried : it also weighs less, and is 

 not so valuable. Cork-tree bark contains a great deal of tannin, but 

 deposits little or no " bloom :" it is therefore generally mixed with other 

 materials, such as English bark or valonea. The tannin it contains is 

 more quickly extracted than from English oak bark. 



" Cork trees are very numerous in Algeria, which country is peculiarly 

 favourable to the development of its precious bark ; for Algeria unites a 

 uniformly high temperature with profuse nightly dews, and the dry, warm, 

 open hill-sides are covered with a sufficiency of light soil. Under these 

 circumstances, cork becomes finer in substance, more elastic, less porous, 

 and freer from earthy particles, than even in Spain, where the best European 

 cork is found." 



" Valonea is the commercial name for the acorn cups of the Quercus 

 JEgilops, a valuable tree which grows in abundance in the Morea and 

 adjacent countries. Several thousand tons of these acorn cups are annually 

 imported into this country from Smyrna and the Morea, and sold almost 

 wholly to tanners and dyers. As soon as the cups are gathered, they are 

 partially dried, and then conveyed by mules to Smyrna, or some other 

 port, from which they are to be shipped, where they are stored in ware- 

 houses for several months, being disposed in layers from 3 to 5 feet in 

 thickness. During this time the cups undergo an incipient fermentation ; 

 and as they dry, the long spreading scales which at first completely 

 confined the acorn become contracted, and allow the acorn to fall out 

 of the cup. When dry, the whole is picked over, to separate the 

 damaged black cups, and all the acorns which contain no tannin. 



" The cups on the surface of the stratum always become damaged during 

 desiccation. The average diameter of the cups of common valonea, including 

 the scales, is a little less than two inches. The quality of valonea may 

 be ascertained by an experienced eye from the appearance of the cup, 

 Avhich when good is thick, full-grown, and of a bright colour. After the 

 cups are gathered, they are frequently exposed to heavy rain, whereby 

 they become deprived of a great portion of their tannin and darkened in 

 colour : they are also frequently injured in preparation for shipment." 



Valonea contains a great quantity of tannin, and deposits a con- 

 siderable amount of " bloom," which gives to the leather a fine buff colour. 



Valonea is usually mixed with bark or other material for tanning sole 

 leather, since if used by itself the leather would be too hard to suit most 

 markets. It is used with gambir for tanning kips and dressing leather. 

 Valonea is an excellent tanning material when used in proper proportions 

 with bark of some sort. In 1856, 22,733 tons of valonea were imported. 

 The average of the three years' imports 1858-60 was 22,000 tons. 



Knoppern is the name given to a peculiar kind of gall which affects 



