f)02 



THE TROPICAL AGBICULTTJTmr 



[June i, 1885. 



decomposition of the organic structure at once takes place : 

 oxygen is absorbed, and carbonic acid gas is given off, 

 generating spontaneous heat amongst the particles of the 

 mass. The rise in temperature increases, as the roll is 

 squeezed together, and would go on until the spores of 

 putrefactive fermentation became developed. This is pre- 

 vented by breaking up the bulk at the proper moment, 

 spreading out the leaf, and exposing it to atmospheric 

 evaporation, which again reduces the temperature. What 

 is now required is a vacuous atmosphere to promote speedy 

 evaporation, for the greater the force of evaporation, the 

 greater will be the degree of cold on the surface of the leaf. 

 AVhat I mean by a vacuous atmosphere is an atmosphere 

 deprived of its own vapour. 



The object in squeezing the leaf into balls is to suspend 

 evaporation and submit it to the influence of sweating 

 caused by the absorption of oxygen and the expulsion of 

 an equivalent volume of carbonic acid gas. This removes 

 the sourness of the leaf by changing a portion of the organic 

 acids into glucose or grape sugar. It may be called a process 

 of insensible fermentation, although it is in reality simple 

 oxidation. True fermentation is caused by the sporules or 

 seeds of living bodies which always float about in the air, 

 and, in entering into the mass of leaf propagate them- 

 selves, and in the act of development cause putrefactive 

 fermentation. If the air of the compartment in which 

 the roll is made could be filtered before passing into 

 it, these sporules would be prevented from entering, and 

 the tea could be preserved for any length of time without 

 the slightest chance of putrefaction. But, on breaking up 

 the rolls, even although they should happen to be over- 

 sweated, if the leaf could at once be exposed to vacuous 

 air, the temperature would be so suddenly reduced by the 

 force of evaporation that any germs of true fermentation 

 which might have been propagated would be instantly 



killed. , 



In the process of rolling and sweating, or so-called fer- 

 mentation, the leaf undergoes a state of oxidation, and 

 becomes darker and darker in color the longer it is exposed 

 to the air previous to firing. This discoloration is caused 

 by the influence of the light and air acting upon the tannin 

 or tannic acid of the leaf. Tannin, which is the astring- 

 ent principle of the leaf, differs from the active prin- 

 ciple— theiue— in chemical composition : the former con- 

 sists of carbon, hydrogen, and oxygen only, while the latter 

 contains a large proportion of nitrogen in addition. 



Tannin in a state of solution rapidly absorbs oxygen, 

 and its astriugency becomes weakened the longer it is 

 exposed to the air by resolution into glucose and 

 gallic acid. In the process of firing, the gallic acid is 

 again split up into carbonic acid gas and pyrogallic acid, 

 or what is termed torihydroxyl benzene. Tannic acid is 

 also formed into pyrogallic acid when heated to 215 de- 

 grees Cent. The former has the property of forming a 

 permanently black oxide with rust, or any ferric substance, 

 and care should be taken that the leaf, from the time 

 that it is picked until it has been fired, is never 

 allowed to come into contact with iron, not even with the 

 head of a nail in the rolling table, as it will leave a black 

 mark on the leaf, which, after infusion, would make the 

 outturn present the appearance of the tea having been 

 burnt in firing, though that should not be the case. 



Tannin is very soluble in water, and in the process of 

 infusion becomes completely dissolved, and should leave 

 the outturn of the leaf a uniform fresh, copper colour. 



Thesoerct of success in the manufactureof good tea, I tiling, 

 lies in expedition— I mean in the processes of of withering, 

 rolling and sweating— for if these are pro- longed, the active 

 principle— theine, consisting largely of nitrogen— volatilizes 

 and Hies off as ammonia gas. Strength, pungency, and flavor 

 can only be preserved by expediting these processes. 



Rapid tiring is, in my opinion, detrimental if the 

 heat, is obtained directly from fuel or from hot 

 air as it commonly exists in the atmosphere, for 

 the simple reason that the astringent principle is burnt 

 out of it by being suddenly exposed to a temperature of 

 215 degrees, changing the tannin into pyrogallic acid, and 

 for the same reason I consider it is injurious to attempt 

 firing more than two or three trays at a time, for the 

 steam arising from the lower trays dissolve a portion of 

 the tannin before it has become fixed, and, besides, the 

 firing of each tray throughout cannot be accomplished under 

 a uniform degree of temperature. 



Speedy fermentation, or sweating of the leaf, depends 

 upon a proper condition of the withering, and this depends 

 upon the hygrometrical condition of the soil and of the 

 atmosphere at the time the leaf is picked. In seasons 

 of drought great attention should be paid to the wither- 

 ing process, for at that time there will be much less sap 

 in the leaf and less moisture to evaporate than would be the 

 case during, or immediately after, rain. Consequently, if 

 the leaf is overwithered, the juice becomes so thick by 

 the time it is ready for fermentation that it will not fer- 

 ment properly, no matter what the condition of the atmo- 

 sphere may be. If the rolling and fermenting operations 

 could be conducted in chambers of dessicated atmospheric 

 air, I do not think it would be necessary to wither leaf 

 more than just enough to prevent it from breaking in rolling, 

 but, until we have special compartments for withering leaf 

 in dry atmospheric air, in wet or dry weather, it is im- 

 possible to lay down any precise rule for guidance. The 

 best test can only at present bo obtained from experience. 



For the process of withering and fermentation, thermo- 

 meters placed in the tea-house, or anywhere, are of no 

 practical use, for the degree of thermal heat indicated by 

 them is no criterion of the general conditions of vapour 

 heat, which exercises the greatest, influence on these oper- 

 ations. With an apparatus to absorb moisture as quickly 

 as it forms, every operation could be carried on with 

 mathematical precision in any kind of weather, but com- 

 mon atmospheric air contains at all times from 50 to 70 

 per cent of the quantity of vapour necessary to saturate 

 it, and, if this proportion does not exist within these 

 limits, the atmosphere is either uncomfortably hot or 

 stewy. R. 



On the principles here enunciated, we feel more than 

 ever convinced of the value of appliances for removing 

 foul and hot air and moisture from leaf-withering 

 and roasting manufactories. The adapted Clerihew 

 is, no doubt, useful, but we know of nothing so 

 rapidly and completely effectual as the Blackman 

 Air Propeller. 



CULTIVATION OF COFFEE, TEA, AND 0IN- 

 OHONA IN MALABAR. 



(From the Field.) 

 Sir, — Now that attention is being directed to the cultiv- 

 ation of fibrous plants, more especially rhea, it may not 

 be out of place to say a few words with reference to 

 such other products as require similar climatic conditions. 

 It has been justly maintained that few districts are 

 better adapted to the cultivation of rhea than Malabar, 

 situated on the Western Ghauts of Southern India. The 

 climate is in every respect suitable, the soil is good, 

 labour is cheap and abundant, and transport charges to 

 and from the coast compare favourably with those of 

 other districts. This applies not only to rhea, but equally 

 so to coffee, cinchona, tea, &c. To commence with coffee. 

 Ah ! but people say, coffee does not pay to cultivate, 

 and upon the face of it, there is much to say in support 

 of this contention ; but it would not be difficult to show 

 that coffee has been made to pay, aud pay well, and 

 that under circumstances as adverse, or even more 

 adverse, than those existing at the present moment. 

 Twenty years ago a planter considered himself a fort- 

 unate man if he got thirty rupees per cwt for his 

 coffee on the coast ; now he would consider him- 

 self very unfortunate iu having to accept that price. 

 Yet today the cost of labour is not greater, while 

 carriage to and from the coast is less. Coffee paid 

 then, why should it not pay now? The. answer is not 

 far to seek, strange though at first sight that answer 

 may appear to be. I say advisedly, the high prices that 

 were experienced some few years ago, and which led to a 

 large area of land being planted which under no condition 

 was suitable for the cultivation of coffee. Somethingalso 

 must be put down to reckless expenditure, the child of 

 temporary prosperity. But what about leaf-disease? I do 

 not believe that I i coffee cultivated nn.l.r conditions not 

 inimical to its growth it will do any materia,! injury, bow- 

 ever fatal it may have been to the class of estates re- 

 ferred to above and worn out properties, of which there 



