256 HEAT REGULATED BY THE 



leaves with activity, but which it becomes neces- 

 sary suddenly and quickly to check, by the appli- 

 cation of intense heat ; as the germination of barley 

 is arrested by a moderate and gradually increasing 

 heat in the process of malting, or the saccharine 

 fermentation in the process of bread-making ; and 

 if Pekoe tea is roasted and dried at a lower tem- 

 perature than any other tea, whether green or 

 black, it is because this tea is made from the con- 

 voluted leaves of the unexpanded terminal bud of 

 the leaf or twig, and has little moisture to part 

 with. Thus, as before explained, young succulent 

 leaves require a high temperature, and dry, old, 

 coriaceous leaves, a low temperature ; so, again, 

 spring leaves more than autumnal. The yellowish 

 green leaves found in fine black tea are doubtless 

 due to similar causes. 



All leaves cannot be gathered of the same age, 

 or under equally favourable circumstances and 

 condition. Thus the yellow or light green leaves 

 found in black tea of fine quality are doubtless 

 due to a higher temperature having been used than 

 was suitable to the condition of those particular 

 leaves, though favourable to the general mass. 

 Sometimes, however, it arises even in spring leaves 

 from too advanced a stage of maturity, their vir- 

 tues being partly lost. Spring leaves especially, 

 and the young leaves generally of black tea, at all 

 seasons of the year, from the course of manipula- 

 tion which they undergo previously to roasting, 



