NOTES ON TANNING SUBSTANCES. 295 



the acorn of the oak in Hungary, and. forms large, crest-like, thick and 

 spongy excrescences. This gall has been figured and fully described in 

 the Technologist, page 183. They are stated to be largely purchased in 

 Britain for tanning leather, but this is not the fact. The common globose 

 galls formed by Cynips Quercus are of no value. It would be very 

 desirable to determine the insect which causes the knoppern. It is 

 generally attributed to the Cynips quercus calycis. Specimens of the oaks on 

 which this acorn are produced show the trees to be the Quercus pedunculated 

 and Q. pubescens. 



Anacardiace^e. — " Trees or shrubs with a resinous, gummy, caustic, or 

 even milky juice. Leaves alternate, simple or ternate, or unecpially pinnate, 

 without pellucid dots, Chiefly natives of tropical America, Africa, and 

 India ; a few are found beyond the tropics, both to the north and 

 south. Pistacias and some species of Rhus inhabit the South of Europe ; 

 many of the latter genus occupy stations in North America and Northern 

 India, and also at the Gape of Good Hope ; and Schinus inhabits 

 exclusively Chile and the adjacent districts. The order is unknown in New 

 Holland." 



The Sumac of commerce is the crushed or ground leaves and stems of 

 Rhus Coriaria, and is imported from Sicily and Malaga, though most comes 

 from Sicily. " It rises to the height of four to eight, and in some cases to 

 twelve feet. Its stem is crooked, and covered with a reddish grey bark : 

 the leaves present a green on the upper, and a whitish colour on the 

 under, surface during spring and summer ; but they assume a reddish hue 

 in autumn." 



a Spanish sumac is variable in quality, being less carefully prepared, and 

 consequently more or less mixed with woody matter ; the best sort comes 

 from Priego, and is grown in the neighbourhood of Malaga. It is like the 

 Sicilian, and affords a colour of equal or greater brightness. With 

 water it gives a darker and more red solution than the former. The other 

 sorts, the Molina and Valladolid sumac, are next in quality to the fore- 

 going." 



In making the ground sumac of commerce, the larger branches or sticks 

 are taken out by hand ; the smaller do not pulverise, and are taken out by 

 sifting ; the stems of the leaves are put under the mill a second time. 

 In grinding, the calculation is that 333 lb. of leaves turn out 280 lb. of fine 

 ground sumac. There is naturally, or at least unavoidably, from three to 

 four per cent, of sand or dirt in the leaves that come from the country, even 

 in the absence of any fraud. This can only be taken out before grinding ; 

 and as the operation makes the sumac cost, if done thoroughly, Is. 6d. per 

 cwt. extra, the trade will not pay the difference, except in some exceptional 

 cases. Sumac is chiefly used for currying and tanning kips for upper 

 leather, and it is also used for dyeing. The average imports of sumac are 

 13,000 to 14,000 tons. 



Schinus Molle. — The leaves and bark of this shrub are used in South 

 America for tanning. . . 



