TANNING SUBSTANCES. 493 



Notwithstanding the number of different substances which have 

 from time to time been introduced for the use of tanners, it is, 

 nevertheless, pretty generally acknowledged that there is nothing 

 superior, or even equal, to good oak bark, and that all attempts to 

 hurry the process beyond a certain point by the use of concen- 

 trated solutions of tan, &c., are for the most part failures, as the 

 manufacture of good leather, to a great extent, depends on the 

 process being conducted in a slow and gradual, but at the same 

 time thorough and complete matter. 



Oak bark is, however, by no means the only astringent bark 

 well suited to the use of the tanner, and in various parts of the 

 world other similar substances are used with very great success. 

 All these tanning materials, though they may not be considered 

 by the English tanner equal to the best oak bark, are, neverthe- 

 less, of great value to him ; they may be employed in conjunction 

 with oak bark, or even as a substitute in times of scarcity, or 

 when the price of oak bark is high ; in fact the very existence of 

 such substances tends to keep down and equalise the price of 

 bark, and to prevent it from undergoing those great fluctuations 

 in value which would necessarily occur were it the only tanning 

 material available to our manufacture ("Prof. Solly in Jury 

 Reports of Great Exhibition.") 



There are a vast number of bark and other substances useful 

 for tanning purposes, which are found in the tropics, that are com- 

 paratively unknown or little regarded in Europe; but which 

 might be readily obtained in large quantities and at a trifling cost. 

 The bark of many species of Acacia furnishes the tanning princi- 

 ple in a great degree, particularly that of A. arabica, which, under 

 the name of Babul wood, is largely used about Scinde, Biliary, 

 Guzerat, and other parts of India ; where it is regarded as a power- 

 ful tonic. The fruit of A. vera, termed Egyptian and Senegal 

 " bablah," has been employed in tanning and dyeing. Numerous 

 species of this tribe are found abundant in New South Wales 

 and the Cape Colony, and these, particularly the wattle bark of 

 Australia, are in common use for tanning, from their astringent 

 properties. The bark and rind of the fruit of the pomegranate 

 (Pumica Granatd) have similar properties. 



The bark of Avicenna tomentosa is in great use in the Brazils 

 for tanning. So are the curved pods of Ccssalpinia Coriari, in 

 the East and West Indies, under the name of Divi-divi. Coriaria 

 myrtifolia is not only used in tanning leather, but also for staining 

 black. It is worth 9 to 10 per ton. Pterocarpus marsupium 

 furnishes about Tellicherry the concrete exudation called kino, a 

 powerful astringent used for tanning. 



The plants of the mangrove tribe, Wiizophora Mangle, and other 

 allied species, have frequently an astringent bark, which is in many 

 cases used for tanning and dyeing black. This tree is very 

 common in most tropical countries, where it forms dense thickets 

 on the muddy banks of rivers and the sea shores. The bark of 



