Of the Excellent Qualities of Coffee. 621 



the operation, and the moment most proper to put an 

 end to it, may be judged and determined with great 

 certainty, not only by the changes which take place 

 in the colour of the grain, but also by the peculiar fra- 

 grance which will first begin to be diffused by it when 

 it is nearly roasted enough. 



This fragrance is certainly owing to the escape of a 

 volatile, aromatic substance, which did not originally 

 exist, as such, in the grain, but which is formed in the 

 process of roasting it. 



By keeping the neck of the globular vessel cold by 

 means of wet cloths, I found means to condense this 

 aromatic substance, together with a large portion of 

 aqueous vapour with which it was mixed. 



The liquor which resulted from this condensation, 

 which had an acid taste, was very high-flavoured and 

 as colourless as the purest water; but it stained the 

 skin of a deep yellow colour, which could not be re- 

 moved by washing with soap and water; and this stain 

 retained a strong smell of coffee several days. 



I have made several unsuccessful attempts to pre- 

 serve the fragrant aromatic matter which escapes from 

 coffee when it is roasting, by transferring it to other 

 substances. Perhaps others may be more fortunate. 



But I must not suffer myself to be enticed away from 

 my subject by these interesting speculations. 



If the coffee in powder is not well defended from the 

 air, it soon loses its flavour and becomes of little value ; 

 and the liquor is never in so high perfection as when 

 the coffee is made immediately after the grain has 

 been roasted. 



This is a fact well known to those who are accus- 

 tomed to drinking coffee, in countries where the use of 



