BAUK FOR TANNING. 155 



In -the second method, the bark is stripped off immediately the 

 trees have been felled. The tree may of course be of any size. If 

 the stems are small enough to be rolled about, they may be peeled 

 in the same way as standing poles, the bark being taken off in 

 complete rolls. In the case of larger stems, the bark must neces- 

 sarily be pulled off in narrow strips like semi-cylindrical tiles ; the 

 bark being thick, with a hard rhytidome, all the incisions must be 

 made with an axe, and in order to loosen it, it has often to bo 

 beaten with the back of the axe. 



In the third method of barking, the tree is cut up into billets, 

 and at any time after the tree has been felled, the billets are ex- 

 posed to the action of steam, under which the bark swells up and is 

 easily detached. It is evident that only comparatively thin wood 

 can be peeled in this manner. Ordinary steam, owing to the solu- 

 bility of the tannin, injures the quality of the bark, and hence the 

 best apparatus are those in which superheated steam is used. Porta- 

 ble apparatus, weighing less than 600 lbs., have been constructed, 

 which, with the labour of only four individuals, give an outturn of 

 more than 2,000 lbs. of bark a day. The researches of Grandeau 

 have proved that the steaming does not affect at all the yield of 

 tannic acid. 



Under ordinary circumstances the bark itself is exported after 

 being dried, in order to reduce its weight and volume and to pre- 

 vent fermentation. Air-dried bark is only from one-half to two- 

 thirds the weight of the green bark. The diminution of volume re- 

 sulting from air-drying varies from 20 to 40 per cent. To dry the 

 bark, the rolls are stood up close together against one another in the 

 form of a pent roof, a line of rolls being placed along the top like 

 ridge tiles ; or they are piled up in a single row, in low stacks, on 

 trestles raised at least a foot from the ground. In fine weather 

 they become sufficiently dry in two or three days. Heavy rain is 

 fatal to the bark, and hence, unless the steaming process is resorted 

 to, drying in the open is out of the question for most of our Indian 

 species, since their growing season is ushered in with continuous 

 wet stormy weather. 



To obviate this very serious drawback, it is matter for consider- 

 ation whether it would not be best to fix the season for felling 

 without reference to the production of tannin, and to extract the 

 tannin at once, thus exporting the extract instead of the very 

 much more voluminous and heavier bark. The extract could be 

 either dry and solid or a thick liquid. In either form the tannic 

 acid would keep for ever, whereas in the bark it disappears in the 

 course of two years in spite of the utmost precautions, and com- 



