FIXED OILS. OLIVE, RAPE, AND LINSEED OILS. 233 



greater or less proportion. That in the greatest request is olive 

 oil ; which is obtained both from the pulpy part of the fruit, and 

 from the seeds ; that drawn from the former source is regarded 

 as the best, being less liable than the other to become rancid. 

 The olive-tree was originally a native of Syria, Persia, and other 

 hot countries in Asia ; but it has gradually extended itself over 

 the South of Europe and the North of Africa. The cultivation 

 of it has been principally attended to in times of peace, of which 

 it was considered as the symbol. It is extremely profitable to 

 the grower, if properly attended to. The young olive-plant 

 bears at two years old ; and in six years begins to repay the 

 expense of cultivation, even if the ground beneath it be not made 

 to yield any other crop. It continues to be profitable for a long 

 period, rivalling the oak in longevity, and bearing good crops 

 when the trunk is reduced to a mere shell ; so that it is a com- 

 mon proverb where it is cultivated, <; If you want to leave a 

 lasting inheritance to your children's children, plant an olive." 

 Olive oil is very extensively used in the south of Europe, in the 

 preparation of various dishes for the table, for consumption in 

 lamps, for the manufacture of the superior kinds of soap, and 

 for various other purposes. It is used very largely in this 

 country, in spite of a heavy duty ; upwards of four millions of 

 gallons having been imported in 1831, of which about half was 

 exported again to other countries. 



371. Rape oil is obtained from the seeds of a species of 

 Brassica, a plant closely allied to the Cabbage, which is culti- 

 vated for that purpose in France and some parts of England. It 

 is much used for burning in lamps ; and has the advantage over 

 others, that it remains fluid at a lower temperature. Linseed 

 oil, which is obtained from the seeds of the Flax-plant, is of 

 very general application in the arts ; especially in oil-painting, 

 and in the composition of varnishes, for which it is particularly 

 adapted by its property of drying on exposure to the air. This 

 power may be increased by boiling the oil, which is then termed 

 drying-oil ; it is in this manner that printer's- ink, which is a 

 sort of paint composed of oil and lampblack, is made to dry 

 rapidly. The seed of the Hemp-plant yields an oil nearly as 



