The following table, given by Dr. Ure, shows the quantity of extractive matter and tannin yielded by different substances:—­

In 480 parts         In 100 parts
by Davy.            by Cadet. 
Sicilian sumach          78                  —­
Malaga ditto             79                  —­
Souchong tea             48                  —­
Green tea                41                  —­
Bombay catechu          261                  —­
Bengal ditto            231                  —­
Nutgalls                127                  46
Bark of pomegranate      —­                  32
"   Virginian sumach   —­                  10
"   Carolina ditto     —­                   5

Catechu and Gambier are very valuable for tanning, and are alluded to under the heads GAMBIER and ARECA PALM.

CATECHU is obtained from the Acacia Catechu, an arboreous tree growing from fifteen to twenty feet high, with a brown and scabrous bark.  The interior wood is brown, dark red or blackish, and the exterior white, one or two inches thick.  It inhabits various parts of the East Indies, of which it is a native, and is also now common in Jamaica.  It bears whitish or pale yellow flowers.

The catechu obtained from this tree in Pegu, is celebrated throughout India, and fetches L4 to L5 more per ton than gambier and other astringent extracts.  When of good quality, catechu is more powerful as an astringent than kino.  Of all the astringent substances we know, catechu appears to contain the largest proportion of tannin, and Mr. Purkis found that one pound was equivalent to seven or eight of oak bark for tanning leather.

The term catechu, observes Dr. Pereira, is applied to various astringent extracts imported from India and the neighbouring countries.  A few years ago the terms catechu, terra japonica, and cutch were employed synonymously; they are now, however, for the most part used in trade somewhat distinctively, though not uniformly in the same sense.  The manufacture of catechu from the Acacia catechu as practised in Canara and Behar, has been described by Mr. Kerr ("Med.  Obs. and Inquiries,” vol. v.), and Dr. Hamilton ("Journey through Mysore,” &c., vol. iii.), while Professor Royle has explained the process followed in Northern India.  According to the last-mentioned gentleman, “the kutt manufacturers move to different parts of the country in different seasons, erect temporary huts in the jungles, and selecting trees fit for their purpose, cut the inner wood into small chips.  These they put into small earthen pots, which are arranged in a double row, along a fireplace built of mud; water is then poured in until the whole are covered; after a considerable portion has boiled away, the clear liquor is strained into one of the neighbouring pots, and a fresh supply of the material is put into the first, and the operation repeated until the extract in the general receiver is of sufficient consistence to be poured into clay moulds, which, in the Kheree Pass and Doon, where I have seen the process, are generally of a quadrangular form.  This catechu is usually of a pale red color, and is considered there to be of the best quality.  By the manufacturers it is conveyed to Saharunpore and Moradabad, whence it follows the course of commerce down the Ganges, and meets that from Nepaul, so that both may be exported from Calcutta.”