TEA MAKING "129 
air. The “ drier” consists essentially of an air-heater, 
and a.drying-chamber through which hot air is drawn 
over the tea by means of an exhaust fan. The tea is 
carried slowly through the chamber on a series of 
moving perforated metal tables arranged one over 
another and so constructed as to resemble endless roller 
shutters. The motion of the individual tables is such 
that the tea travels from the top of the chamber to the 
bottom, where it is discharged. The temperature of 
the air entering the drying chamber is usually between 
220° F. and 240° F., but when the firing is about 
three-quarters completed, the temperature is lowered to 
180° F. or 200° F. The time required for the drying 
is usually about twenty-five minutes. 
With the completion of the firing the tea is made. 
Subsequent processes of grading, ‘‘ equalising,” packing, 
etc., need not be considered here, except to mention 
that previous to packing, the tea is subjected to a final 
firing to complete the drying. 
THEORY OF TEA MANUFACTURE 
It will be obvious that the key-phase of black tea manu- 
facture is the fermentation process. Indeed, it is recog- 
nised that virtually everything prior to fermentation is 
tributary to that process, and adapted to give it full scope; 
while the subsequent stages of manufacture are to control 
the fermentation and take full advantage of its results. 
The scientific work which has established this position is 
due chiefly to the following British and Dutch chemists, 
viz. Bamber, working in Ceylon ; Mann and Hope (3), 
of the Scientific Department of the Indian Tea Associa- 
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