Tar -making : Pitch : Lamp-black, etc. 203 



Tar-manufacture. 



809. In making charcoal from highly resinous woods, tar is pro- 

 duced, in notable quantities ; and for collecting this a circular floor 

 of masonry is prepared, sloping to a central point, from whence it 

 flows out through a pipe into a reservoir on one side from which it 

 may be dipped. 



119. Foundation of a Tar-kiln, in which a, ft, is n sloping brick or stone hearth, 

 with a grating ut <t, through which tin.; tar I>U<M-<. ami is conducted by the 

 pipe, It, to the rcsurvoir, c. 



810. By a more slovenly and wasteful process, the tar is allowed 

 to ooze out iut<> gutters in the soil, and is led from these into barrels 

 sunk in the ground. 



811. In the more refined methods of tar-making, the knots, resin- 

 ous wood, or refuse products of the turpentine works are put into 

 large iron receivers set in masonry, so that heat may be applied ex- 

 ternally by fire in an arch. A pipe leads from the bottom of these 

 receivers for carrying off the tar. Another pipe, near the top, 

 conducts away the volatile portions, which are condensed, as in 

 common distillation. 



812. Pitch is simply tar boiled down till it will become solid when 

 cold. Its principal use is in ship- building, for rendering the seams 

 under water and the rigging exposed to the weather impervious to 

 water. It is also used in roofing and elsewhere for similar pur- 

 poses. 



813. Lamp-black is the smoke of resinous woods, or of the refuse 

 strainings of rosin. When these are burned, the smoke is passed 

 into the chambers lined with coarse cloths, which allow the gases to 

 escape, but intercept the carbonaceous portion, which is collected 

 from time to time. 



814. Canada Balsam is obtained from the blisters that form in the 

 bark of the Abies balsamea, or balsam-fir, found growing in the 

 swamps of the Northern States and in Canada. It is used medicin- 

 ally, and is an officinal article in the pharmacopoeias. Among other 



