24 



from the green colouring material. They are formed 

 by a process of oxidation which does not take place till 

 the cells of the leaf are dead. As soon, therefore, as 

 portions of the leaf die, they at once begin to turn brown, 

 provided sufficient moisture is present. The two essen- 

 tials for the development of the brown colour are a supply 

 of oxygen, which is obtained from the air, and a sufficient 

 amount of moisture. This development of the brown 

 colour, which is begun in the second stage of curing, is 

 always completed in the fermentation of the tobacco ; 

 and the chief danger as regards the curing is that the 

 development will proceed too far because of excessive 

 moisture, causing the leaf to cure too dark. 



As regards quantity, the most important change in 

 the curing is the loss of water. The tobacco leaf nor- 

 mallv loses about 75 per cent. <>f its green weight in the 

 curing, and by far the greater portion of this loss in 

 water. To cure tobacco successfullv, this vast amount 

 of water must be removed under such conditions and at 

 such a rate as will best allow the other important changes 

 to take place. In the second stage of the curing, when 

 the leaf begins to turn brown, the relative humidity may 

 be lowered from X;, per cent, of the first stage to about S> > 

 per cent., and then the latter still further reduced to -o or 

 0; per cent., until the stems are dry. If the humidity 

 remains \crv high at this stage tor any considerable 

 period, pole-sweat will surely develop. This is to be 

 especially leared if a season of warm, moist weather sets 

 in, and mav soon render the entire contents of the barn 

 praelieallv worthless. The only remedy lies in the use 

 of artificial heat to keep down the humiditv Ventila- 

 tion alone will be of little a\ ail. Ivitiivlv aside from tin 

 danger of pole-sweat, however, there ire other impor- 



