FIXED OILS. 197 



its quality. The latter consideration does not deter 

 some cultivators from employing this preliminary 

 process in the extraction of the better kind of oil ; 

 a practice which, however, proves extremely prejudi- 

 cial to the product, to obtain which, of the best 

 quality, the fruit should be pressed immediately after 

 it is gathered. 



Olive oil when extremely good and pure can be 

 preserved for several years, but such a quality is 

 very rare, and in general olive oil deteriorates after 

 being kept any length of time, losing its limpidity 

 and becoming rancid. If the olive be not sufficiently 

 ripe when expressed the oil will be bitter, if it be 

 too ripe the oil will be thick and glutinous. The 

 method of extracting the oil has likewise a great 

 influence on its quality. 



Olive oil becomes solid at 10 of Fahrenheit. Its 

 specific gravity is * 913. It is never used in the com- 

 position of paints as it does not dry completely. 

 The olive-tree produces oil abundantly, and a planta- 

 tion of this in a favourable climate is always a certain 

 source of profitable industry. "The young olive- 

 plant bears at two years old, in six }ears begins 

 to repay the expense of cultivation, even if the ground 

 is not otherwise cropped. Alter that period, in good 

 years, the produce is the surest source of wealth 

 to the farmer, and the tree rivals the oak in lon- 

 gevity, so that the common proverb here is, * If 

 you want to leave a lasting inheritance to your 

 children's children plant an olive.' There is an old 

 olive-tree near Gericomio which last year yielded 

 two hundred and forty English quarts of oil ; yet its 

 trunk is quite hollow, and its empty shell seems to 

 have barely enough hold on the ground to secure it 

 against the mountain storm *." 



* Three Months passed in the Mountains East of Rome during 

 the year 1819, by Maria Graham. 



s 3 



