194 VEGETABLE SUBSTANCES- 



CHAPTER XII. 

 VEGETABLE OILS AND SIMILAR PRODUCTS. 



FIXED OILS.' OLIVE RAPE LINSEED HEMP COT- 

 TON SESAMUM RAPHANUS ARACHIS POPPY 



NUT BEECH PALM COCOA-NUT BEN. 



VEGETABLE oils are distinguished into two kinds, 

 fixed or fat oils, from which no vapour is given off at 

 the temperature of boiling water, and volatile or 

 essential oils, which give off vapour at that tempera- 

 ture with water, or under 320 by themselves. 



Those of the first class are obtained by expression 

 principally, if not entirely, from the fruit or seed of 

 plants. A variety of seeds are more or less oleagi- 

 nous, more especially those of the nut kind, from all 

 of which oil may be extracted. Many of the oils of 

 this description are applicable to the arts, or are 

 employed in combustion for producing light. 



The vegetable oil most known and esteemed is 

 that expressed from the olive. An account of this 

 valuable tree has been already given in a former 

 volume, where the extent of its cultivation and the 

 manner in which it was prized by the ancients have 

 been fully dwelt upon. 



The olive s which now appears a native production 

 of Italy, luxuriating in its genial soil and climate, is 

 not however indigenous to that country. Pliny, 

 who largely discourses on this tree and its produce, 

 notices its first introduction, whence the historian of 

 Rome remarks, " The olive in the western world 

 followed the progress of peace of which it was con- 



