286 CHEMICAL CAUSE 



quantity of apothem is only 1*48, whereas the 

 loss of tannin is about 30 per cent, of the whole 

 quantity. 



To whatever cause this loss of tannin in black tea 

 may be due, in that will be found, I am disposed 

 to think, the true solution of the difference between 

 black and green tea. That this loss does not 

 depend on difference of temperature, or different 

 amounts of heat, has been abundantly proved. It 

 is then in that process which the black tea leaves 

 undergo previous to roasting, during which they 

 are treated as hay, that the true cause must be 

 sought. 



This process (To Ching) has been aptly termed 

 " withering." It is in fact incipient change, fer- 

 mentation, or eremacausis. In a state of decay 

 all organic substances absorb oxygen from the 

 atmosphere, which, acting on the azotised elements 

 contained in these bodies, sets in motion a new 

 arrangement of their constituent parts ; absorbing 

 oxygen and evolving carbonic acid. There are 

 certain groups of vegetable substances also, whose 

 constituents are the same, varying only in their 

 quantity of the elements of water. These are held 

 together by very feeble affinities ; so that certain 

 transformations from one to the other easily take 

 place. Starch, Cane sugar, Gum, Sugar of milk, 

 and Grape sugar constitute one of these groups. 

 The ease with which starch is converted into sugar 

 is seen in the process of germination in the malting 



