EMPYREUMATIC OILS 235 



vessel for receiving the oil is sunk in the earth im- 

 mediately beneath this aperture. This vessel or 

 receiver has a wooden cover, with an opening 1 in the 

 middle and channels cut in it. The bark is gathered 

 into a heap and pressed into these pits, and after be- 

 ing covered with turf is set on fire. The oil-distilling 

 through the hole at bottom drops into the vessel 

 prepared for the purpose. After being thus obtained 

 it is put into casks made of the hollowed trunk of a 

 tree. The pure limpid oil which floats on the top is 

 used in the preparation of leather, for which purpose 

 it is in great request on account of its. antiseptic qua- 

 lities. To this oil Russia leather owes its peculiar 

 smell*. 



In woody regions, where the peasantry trade in 

 birch oil, immense pits are made ; the cover of the 

 vessel placed at bottom is made distinct and indepen- 

 dent of the vessel itself, in such sort that the vessel 

 can be removed at pleasure without disturbing the 

 cover. To this space beneath a subterraneous pas- 

 sage is made, into which the people can creep and 

 place the vessels, and, when filled with oil, replace 

 them with other receivers. 



Tar, which is so extensively used for naval pur- 

 poses, may likewise be classed with the impure em- 

 pyreumatic oils. 



It is distilled from the wood of the fir-tree, and 

 produced in large quantities in the north of Europe 

 and in North America. We receive it from Russia, 

 Sweden, and America; that coming from Sweden 

 being considered the best, and commanding the 

 highest price. 



Great part of that which is manufactured in Ame- 

 rica is made from old fir-trees, which have fallen 

 down in the woods, and have their sap no longer 

 * Pailas's Travels Letters from Scandinavia. 



