LIMITED BY EVAPORATION. 253 



fell rapidly to 170°, and continued to fall slowly. 

 Thus taking the mean of the extremes of the cold 

 and hot thermometers 138° and 170° equal to 

 154°, the temperature thus given very little exceeds 

 the point at which steam is said to scald. Hence 

 it seems to me conclusive that, agreeably to the 

 mode of manipulation practised by the Chinese, a 

 very high temperature may be used without in- 

 curring the risk of raising the heat of the leaves 

 to any degree approaching the boiling point ; and, 

 consequently, agreeably to the commonly received 

 opinions of scientific and practical men (as a 

 general rule), without injury to the aroma. Indeed 

 it may be doubted whether there be any connexion 

 between the heat employed and the amount re- 

 ceived by the leaves ; that is, whether the leaves 

 have the power to receive above a certain amount 

 of heat, so long as copious evaporation be main- 

 tained. Analogy seems to favour this doubt. 

 Fluids in undergoing the change from a liquid 

 to a gaseous state send or carry off all superabun- 

 dant heat, and thus is kept down the temperature 

 of the body from which they emanate. Thus the 

 temperature of the body and blood cannot be 

 raised much above 98° or 100°*, so long as copious 

 perspiration be maintained ; nor can water be 

 raised beyond 212° under the ordinary pressure 

 of the atmosphere — or ether above 98° f, and so 



* Brande's Manual of Chemistry, p. 1337. 

 t lb. p. 1278. 



