294 HISTOEY AND DETAILS OP WHALING. 



varieties of oil are darker than others, which requires addi- 

 tional labor in this respect. 



There is another method, and usually the ordinary one, by 

 which oils are clarified and prepared for the market. It is 

 termed panning. 



For this purpose, after it has been bleached, strained, or 

 pressed, and it does not assume the right color or shade, it is 

 pumped into large, leaded, superficial vats, or pans, located in 

 a building near by, whose side roof is wholly of glass, like a 

 glass house, and so arranged that both air and sun can act upon 

 large bodies of oil in different stages of whitening. 



This process not only whitens the oil, but whatever particles 

 or thickness there may have been in the oil, not discernible 

 before, is now all removed and deposited on the bottom of the 

 pan. The oil taken from these pans is put into barrels or casks, 

 and is ready for the market. 



Government Test of Sperm Oil. The lighthouses upon 

 our seaboard, and also upon the lakes, are furnished with the 

 best quality of sperm oil. 



Sperm oil has a standard weight established or recognized 

 by the government, and according as varieties fall short or go 

 beyond this measure, or standard, indicated by a nicely ad- 

 justed oilometer, its true weight and value are ascertained. 



Winter strained sperm oil is heavier, and burns away faster 

 than spring strained sperm oil, for the simple reason that the 

 winter oil is freer from spermaceti than the spring strained oil. 



Sperm oil is tested by authority of government, when con- 

 tracts are made with the manufacturer to furnish oil for light- 

 houses, in the following manner : A common tin lamp of 

 a cylindrical form is taken, and fitted with a wick which 

 reaches to the bottom of the lamp. It is then filled with oil, 

 and kept burning until all the oil in the lamp is burned up, 

 and the wick so dry that not a drop of oil will fall from it. 



The number of hours which a given quantity of oil will 

 burn, is another consideration included in determining the rel- 

 ative quality of oil. 



