194 



DOMESTIC BOTANY. 



hole is dug in the ground, generally in the side of a bank, 

 in which the billets are placed and formed into a heajD 

 above the surface, the whole being closely and compactly 

 covered with turf or earth, a fire is then kindled from be- 

 low and the slow combustion causes the tar to exude from 

 the wood, and IIoav from an opening into barrels placed below 

 to receive it. The greatest quantities used in this country 

 are imported from the United States, from ports in the 

 Baltic, and Archangel. Tar by distillation yields the pro- 

 ducts wood vinegar (pyroligneous acid), oil of tar, and 

 creosote, and leaves a resinous residue called common pitch ; 

 the principal quantity of pitch, however, is obtained by 

 boiling tar ; by evaporation the volatile oil passes off, and it 

 hardens. 



The above method of obtaining tar and pitch was described 

 by Theophrastus 2200 years ago. Turpentine is the fluid 

 juice of fir trees, which flows freely when wounds are made in 

 the bark. It is composed of volatile oil and resin, and hence 

 is termed oleo-resin, but by distillation their component 

 parts are separated ; the former constitutes what is called 

 oil of turpentine, and the latter the well known resin. The 

 greatest quantity of turpentine used in this country is im- 

 ported from America. 



Pinus Pinaster^ P. Laricio and P. maritima. All natives 

 of Southern Europe. They are planted on the low shore in 

 the West of Ireland, Normandy, and other places for fixing 

 the sands, where they form a thick low bush, but in favour- 

 able situations they attain the size of lofty trees. The first- 

 named produces Bordeaux turpentine. 



Stone Pine (Pinus Pinea). A low bushy tree, native of 

 the South of Europe, growing freely in this country. The 

 seeds are large and nutty, and are eaten. There are many 

 Pinuses of value in their native countries for their timber, 

 such as P. Lambertiana, P. Coulterii, P. Sahimana, P. ma- 

 crocarpa^ and P. ponderosa, all large trees of California and 

 North West America. Their nutty seeds form the principal 



