236 VEGETABLE SUBSTANCES. 



fluid. This is what is called light-wood, not with 

 reference to its weight, as it is very heavy, but from 

 its combustible nature, readily igniting 1 and burning 

 with so bright a flame as to serve the office of a 

 candle. Only one particular species of pine (pinus 

 palustris) becomes light-wood. Persons concerned 

 in making tar immediately know it from the appear- 

 ance of the concrete juice in the grain of the wood. 

 When fir-trees are to be cut down for this purpose, 

 those are most esteemed whose branches are dis- 

 torted and full of knots ; the sap which is thereby 

 retarded in its circulation depositing a better kind, 

 as well as a greater quantity of the resinous matter 

 from which tar is distilled. Old trunks of trees, 

 which have remained in the ground many years after 

 their branches have been cut off, are likewise rich in 

 that material. But the surest and best method of 

 obtaining the greatest quantity of tar- wood, is to 

 strip off the bark and branches in the spring from 

 such firs as are destined for this purpose, and to 

 leave them in that state until the year following. 

 They should then be felled, and cut into small pieces 

 as if for fagots. Being well dried, those billets 

 which appear most oily and resinous are separated 

 from the rest, and alone reserved for use ; two-thirds 

 or more of the tree will be thus retained, provided 

 it was in a state of proper maturity previously to the 

 stripping of the bark, and that after this operation it 

 had been left sufficiently long in the ground. This 

 is called tar-wood. The wood of the trees from 

 which turpentine has ceased to flow is likewise made 

 to yield tar. The faces over which the juice has 

 flowed and partially concreted are split off, and from 

 these is made what is called green tar, because dis- 

 tilled from green wood instead of dry. 



When a sufficient quantity of wood is collected, 

 a circle is marked out on the ground for the kiln. 



