3 66 THE POPULAR SCIENCE MONTHLY. 



during the fermentation in the manufacture of black teas. But it is 

 important to know that only a small part of this tannin is extracted 

 from the leaf in the suitable preparation of the beverage. Some ex- 

 periments with tea as it is prepared for the table gave, for a five fluid- 

 ounce cup of the liquid, in ten instances an average content of a trifle 

 over one grain of tannin. Other experiments with tea after five min- 

 utes' steeping gave in twelve instances an average of tannin equal to 

 only yf T per cent of the dry leaf ; while the same teas, on thirty min- 

 utes' gentle steeping, yielded tannin amounting to an average of 2^ 

 per cent of the dry leaf. In another case, by thirty minutes' active 

 boiling, so much tannin as 11-| j)er cent of the tea-leaf was obtained 

 in solution. Black teas are necessarily steeped longer than green, as 

 they yield all their soluble matters more slowly. In coffee the propor- 

 tion of tannin is not over one third, perhaps on an average not over 

 one fourth or one fifth, of that in tea. The cacao-nib and its prepara- 

 tions are free from tannin. Guarana is heavily charged with a specific 

 variety of tannic acid, and the mate is even more astringent than the 

 tea-leaf. 



The fragrant principle of tea, the essential oil, already referred to, 

 has not been separated in notable quantities, but it is recognized as a 

 diffusible stimulant, transient and harmless in its effect on the system, 

 and certainly attracting no little favor to the tea-cup. The diffusible 

 flavorous substance of coffee is a product of its roasting, and the same 

 is true of the proper fragrance of cacao, to which other odors are often 

 added. These vaporous bodies are so easily dissipated by a pi-olonged 

 steeping, and especially by an active boiling, that brief infusions of tea 

 and of coffee are likely always to be preferred. 



In the quantity of the alkaloid, theine or caffeine, the tea-leaf is 

 over twice as rich as the coffee-berry. The medium proportion is that 

 of 2 to 2^ per cent in tea, a little under 1 per cent in coffee, and about 

 1 per cent (theobromine) in the cacao-nib while the guarana prep- 

 aration has 5 per cent, and the mate H per cent. Attfield found 2 per 

 cent of alkaloid in the cola-nut. From a pound of tea, then, there can 

 be obtained at least 140 grains, or over a quarter of an ounce, of the 

 crystallized alkaloid, about enough to balance a silver quarter-dollar 

 and a dime. The theine in a pound of tea is twenty-five or thirty 

 times as much as could be taken at once without notable disturbance 

 of the nervous system. A pound of coffee contains twelve or fifteen 

 times as much theine as one ought to take at once. 



The greater portion of the alkaloid enters into solution in making 

 the common hot infusions of coffee and tea. Tea yields its alkaloid to 

 hot water upon even brief application ; coffee, especially when but 

 lightly roasted, requires longer steeping for the extraction of the 

 theine. It may be said, then, of long steeping of coffee and tea, that 

 it is not required in obtaining the chief portion of the stimulant prin- 

 ciple ; that it only serves in the case of coffee to increase somewhat 





