254 ABSORPTION OF HEAT BY LEAVES 



on. So tea and other leaves, according to their 

 succulency and viscous qualities, may have their 

 determinate amounts of heat, so long as copious 

 evaporation continues ; and this, in the case of tea 

 leaves, seems to be between 150° and 170° 

 Fahrenheit at this particular stage of the process. 



Thus the rapid evolution of steam and the 

 copious moisture with which the leaves are covered 

 and surrounded, must be considered as the cause 

 of their not burning. The dexterity of the work- 

 man, doubtless, has much to do in preventing this 

 evil. The mode of manipulation, as already de- 

 scribed, the constant stirring about the leaves in 

 the vessel ; the new surface, which is ever presented 

 to the heated part of it ; the raising them in the 

 air, shaking them on the hand, and scattering them 

 loosely in the fall, are all expedients of the roaster 

 to dissipate the steam, to spare his hands, and to 

 keep down the temperature. 



Upon trying a similar experiment in the drying 

 tube, or poey long, used in the process of drying 

 black tea, I found that when one thermometer, 

 placed in the sieve immediately over the fire, 

 marked 250° of heat, the leaves, suddenly raised in 

 the same manner as just described, indicated, with 

 a cold thermometer, a temperature of 179°; thus 

 showing, as might be expected, that as the leaves 

 part with their moisture, their capacity for heat 

 increases ; and all agree that it is in the process of 

 drying, when a comparatively low temperature is 



