252 POPULAR ECONOMIC BOTANY. 



and packed, of the wood of the roots of the pine ; the mass 

 is then ignited and covered over with soil. Combustion is 

 thus carried on very slowly, and the tar which distils runs 

 down the sides into the iron pan, and is given off through 

 the spout, from which it is received into barrels. Nearly 

 all the tar we receive from abroad is from Eussia and Nor- 

 way. In 1851 it amounted to 12,096 lasts measure, or 

 about 24,000 tons weight. Tar is about the colour and 

 consistency of treacle, and is used chiefly for the purpose 

 of preserving cordage and wood from the effects of the 

 atmosphere. 



Pitch is procured by distillation from tar, in the same 

 manner as rosin from turpentine. It is a black, solid, and 

 glossy substance, with a brittle, shining fracture ; it is used 

 for similar purposes to tar, with which it is often mixed, 

 and also for caulking the seams of vessels; it was well 

 known to the ancients. The pitch used in this country is 

 mostly home-manufactured. Natural evaporation of the 

 volatile portions of tar will of course convert that product 

 into pitch. 



Asphalte is fossil pitch. 



The two next substances, though they are not, strictly 

 speaking, gums or resins, are nevertheless inspissated juices 



