TANNER'S BARK. 



TAR-ROOT. 



coats of plaster, and the workmanship is exe- 

 cuted like field walls at 10s. per 100 square 

 feet; the only essential being that no clay be 

 used (which worms in time bore through), and 

 that the lime, or Parker's cement, be good. 



A current of air is said to promote the purity 

 of water in tanks, which is easily effected by 

 the earthenware or other pipe which conveys 

 the water from the roof being of 6 or 8 inches 

 in diameter, and an opening left for the surplus 

 water to run away; and where the prevailing 

 winds do not blow soot and leaves on the house, 

 the water remains good, even for drinking, with- 

 out clearing out the rubbish more than once a 

 year; but, in some cases, filtering by ascension 

 may be found useful, and effected by the water 

 being delivered by the pipe at the bottom of a 

 cask or other vessel, from which it cannot 

 escape till it has risen through the holes in a 

 board covered with pebbles, sand, or powdered 

 charcoal. See RESERVOIRS, PO.VDS, &c. 



TANNER'S BARK. The bark of oak, 

 chestnut, willow, larch, and other trees, which 

 abounds in tannic acid, and is used by tanners 

 for preparing leather. After being exhausted 

 of the tanning principle by being chopped into 

 small pieces, or bruised and steeped in water, 

 it is laid up in heaps to dry, and sold to gar- 

 deners for the purpose of producing artificial 

 heat by fermentation in pits or beds, in bark- 

 stoves or other out-houses. See BARK and 

 FARM-YARD MANURE. 



TANNIC ACID. This term has been espe- 

 cially applied to a substance obtained by Pe- 

 longe, by acting upon bruised galls by common 

 unrectified ether, in a long, narrow funnel or 

 percolater. Tannic acid is a white uncrystal- 

 line powder, very astringent, little soluble in 

 water, and reddening litmus. When moistened 

 and exposed to air, it attracts oxygen, is de- 

 composed, and is converted into gallic acid. 

 It is extremely astringent, and appears to be the 

 active principle of tanning substances (tannin) 

 in general. Its ultimate elements are 30 atoms 

 of carbon, 18 of hydrogen, and 24 of oxygen. 



TANNIN. A word synonymous with tannic 

 acid, the pure astringent principle upon which 

 their power of converting skin into leather 

 depends. Its leading character is its property 

 of producing a dense whitish precipitate in a 

 strong solution of animal jelly, such, for in- 

 stance, - as isinglass; and on this account it 

 condenses the gelatin of animal hides, and, ren- 

 dering them impermeable to water, converts 

 them into leather. It may be obtained tolera- 

 bly pure by infusing bruised grape-seeds in 

 cold water, or more circuitously by adding 

 acetate of copper to filtered infusion of galls, 

 washing the precipitate, and decomposing it 

 (diffused through water) by sulphuretted hy- 

 drogen. On evaporating its solution, it is 

 obtained as a pale yellow extract of a strong 

 astringent taste. The action of astringents 

 upon persalts of iron has given rise to its dis- 

 tinction into two varieties, the first changing 

 them to deep blue or black, the second to green. 

 The tan of galls, oak, bark, grape-seeds, &c., 

 possesses the former property ; that of catechu 

 and tea, the latter. (Brandos Diet, of Science.} 



TANNING. The art of preparing leather 

 from raw skins and hides so as to render them 

 1032 



more pliant, durable, and impermeable to 

 water. The processes employed for this pur- 

 pose are various, every tanner adopting some 

 peculiar or favourite method. 



A discovery has recently been made which 

 seems likely to revolutionize the tanning trade. 

 By means of a tanning machine, or pair of 

 horizontal rollers fixed over a tan-pit, between 

 which is fixed a band or belt of hides attached 

 by ligatures to each other, to the number of 50 

 to 100, and by which the rollers are constantly 

 fed or supplied, the hides are lifted out of the 

 pit on one side of the machine; as they pass 

 between the rollers, the exhausted ooze or tan- 

 ning liquid is pressed out of them, and they 

 are deposited in folds in the pit on the other 

 side of the machine, where they absorb another 

 supply of fresh tannin. The first hide having* 

 been inserted between the rollers, the others 

 follow in succession, and upon arriving at the 

 end of the band the motion of the roller is 

 reversed, and the belt is returned through the 

 machine to receive another squeeze. This al- 

 ternating motion is constantly repeated, the pit 

 being replenished from time to time with fresh 

 solutions of tan, till the operation is completed. 

 The effects produced by this simple plan, are 

 1. The shortening of the time of tanning to 

 one-fourth of that generally required. 2. The 

 production of a considerable increase of weighU 

 3. The leather tanned by this method resists 

 water longer than that tanned by the old pro- 

 cess. 4. The new method is cheaper than the 

 old. 5. It is applicable to the existing tan- 

 yards, at a comparatively trifling expense, with 

 a capability of working in rounds or series, and 

 of expending tan or liquor. 6. That it is availa- 

 ble for all sorts of leather. 



TANSY (Tanacetum). The species of tansy 

 are not possessed of much beauty. The hardy 

 kinds succeed in any common soil, and are 

 readily increased by rooted slips of the fibrous 

 creeping root. They increase freely by cut- 

 tings. Withering asserts that if meat be rubbed 

 with the leaves of tansy, the flesh-fly will not 

 touch it. In England the only indigenous spe- 

 cies is the common tansy (T. vulgare). Every 

 part of the herb is bitter, with" a strong but not 

 unpleasant scent. The qualities are esteemed 

 of a tonic and cordial nature, expelling intes- 

 tinal worms, and strengthening the digestive 

 powers. The plant, however, does not agree 

 with every stomach. There are two varieties 

 of this species, the variegated, and the curled 

 or double tansy, which is kept for use in gar- 

 dens, as being more wholesome or milder than 

 the wild sort ; but in England tansy pudding is 

 out of fashion. 



TAPE-GRASS or EEL-GRASS. See VA- 



LESXERIA. 



TAPIOCA. A white, edible substance, con- 

 sisting of very pure starch, obtained from the 

 root of a tropical plant called manioc (Jatropa 

 manihot) or cassava. 



TAP-ROOT. A root which penetrates deep 

 and perpendicularly into the ground without 

 dividing, and has few lateral fibres. In shape 

 it resembles a spindle ; hence it is botanically 

 termed a fusiform root. But the main trunk 

 of any root that penetrates vertically deep into 

 the ground is called the tap. 



