240 VEGETABLE SUBSTANCES. 



The quantity of tar retained forborne consumption 

 in 1830 was 5,205 lasts. It is admitted from foreign 

 countries on a duty of fifteen shillings per last, an 

 abatement of three shillings per last being made on 

 that coming from British possessions. The price of 

 tar varies from fifteen shillings to seventeen shillings 

 per barrel. 



Pitch, which is condensed tar, is obtained either 

 by evaporation or burning. The process of burning 

 is performed very simply. A hole is dug in the 

 ground and lined with brick : it is then filled with 

 tar, which is ignited and allowed to burn till the 

 pitch is judged to be of sufficient consistency, which 

 is ascertained by dipping a stick in it, and allowing 

 the pitch adhering to it to cool. When sufficiently 

 burnt the hole containing the pitch is closely covered, 

 and the atmospheric air being thus excluded, com- 

 bustion ceases. Five barrels of green tar are thus 

 concentrated to two barrels of pitch, and two barrels 

 of other tar make one of pitch*. 



When pitch is evaporated in kettles it requires to 

 be almost constantly stirred. The country people in 

 Sweden, when they have no kettle for boiling their 

 tar, in order to reduce it to pitch, put it into great 

 wooden pails : into these pails they throw very large 

 stones previously heated ; the stones keep the tar 

 almost boiling, and this process is continued until 

 the fluid is of sufficient thickness. 



A portion of the tar imported into this country is 

 converted into pitch : the establishments for this pur- 

 pose near London are conducted on a much more 

 economical plan than that pursued abroad. Here 

 no part of the tar which has any useful property is 

 allowed to be wasted. It is evaporated in a still, 

 and consequently the valuable volatile products are 

 * Trans, of S. for the En. of Ars., &c. 28th vol. 



