QUALITY DEPENDENT ON VARIOUS CAUSES. 805 



teristic colour of this tea, which it gradually ac- 

 quires in this process, and which resembles the 

 bloom on some fruits. This peculiar colour is the 

 result of a quick evaporation of the fluids, and the 

 admission of light and air to every part of the 

 leaves ; and which, it is surmised, may work certain 

 chemical effects altogether sufficient to account for 

 the different results in this process. The essential 

 oil of green tea, on which its aroma depends, ap- 

 pears to be developed, as in coffee, solely by arti- 

 ficial heat. 



Thus the various known differences in tea may 

 now be classed in the following order : — 1 . Dif- 

 ferences arising from natural causes, — as the age 

 of the leaf; for instance, the unexpanded convo- 

 luted bud of the leaf, as in Pekoe tea and Long- 

 csin tea, the one a black and the other a green tea; 

 — the fully expanded, though young leaf, in all 

 other teas ; — the young and succulent leaves being 

 only fit for tea : — and, the season of gathering, the 

 spring leaves being the best, and the autumnal the 

 worst. 



2. Differences occasioned by atmospheric in- 

 fluences, as the state of the weather or season ; 

 the presence or absence of sun, rain, &c, in com- 

 mon with all other vegetable productions. 



3. Differences caused by various modes of mani- 

 pulation, as the treatment of the leaves of black tea 

 as hay previously to roasting ; — - a difference in the 

 processes of roasting and drying certain black teas, 



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