February i, 1884.] 



THE TROPICAL AGRICULTURIST. 



543 



citrrent of hot air through parchment spread on lofts. 

 In utilizing the idea for dispelling moisture from cin- 

 chona bark Mr. Cameron suggests alterations which 

 would economize fuel. We do not suppose that any 

 patent rights survive in the case of the Clerihew, 

 but we are not quite so certain that Mr. Cameron 

 may not be trenching on the domain of some patentee 

 in his suggestion.s for manufacturing and applying 

 dry air for the withering of tea leaf. We hope not. 

 however. A practical trial alone can decide the real 

 value of the means proposed, but we believe that 

 moderate, diffused artificial heat helps the process of 

 withering in damp weather, whil" there can be no 

 question of the value of as much light as can be 

 secured iu tea-houses by the liberal employment of 

 glass. 



KEMAUKS ON HOT-AIR CINCHONA 



BARK DRIER. 



{Ftom the Proceedings of the Dimhuhi Planters' 

 Associaiion.) 



22nd November 1883. 



Mr. (Jhairmau aiul Gentlemen, — Being unable to liepre- 

 sent at the late meetiugs, when cinchona stati.-itics, niudos 

 of harvesting the bark, &.C., were discussed, I promised our 

 Secretary a lew remarks on curing bark, as soon as X bad 

 comijleted a new drying apparatus then in progress. I 

 now redeem my promise. 



It is ahnost supertiuous to notice that for drying ciu- 

 chuiia bark and most otlier products of the kind, ibfre 

 is likely no way so good as laying the substance to be 

 dried iu the sun. It is equally so, to nmark, that in our 

 wetter districts for months on end, there is no suu-drj-ing 

 available^rain, mists and clammy damp prevailing. 



Such being the conditions under which some of the pro- 

 ducts of tliis prolific island have to be harvested, it be- 

 comes an important consideration, how curing may best be 

 done by the u.se of fire heat, wiiich can be employed for 

 tiiis purpose eificieutly in a variety of w:iy.s. Dismissing 

 all other considerations for the moment the matter 

 resolves itself into the simple ([uestiou of economy : 

 first, ctfeetive performance of tlic work, second, the 

 cost. This granted, we have now to go directly 

 into the subject from a mechanical point of view. I'lre- 

 heat employed directly will not answer our purpose. It is 

 all very well for drying our clothes or boiling our kettles, 

 but iu the case of bark and other products, bulky masses 

 of material have to be dealt with, and it is not mere 

 heat or stewing that can be effective ; but for the pur- 

 poses of conservancy, the moisture must be driven otf or 

 removed as completely as possible. To do this properly, 

 we must expose the largest amount possible of the 

 surface of the materials to be dried,, to the drying 

 influence. As this could be but small at an ordinary lire, 

 we are thus led to using air already heated, or dried 

 iiaUed, if the arrangtmeuLs are suiiiciently elaborate. 



Without at all attempting to go into this subject 

 deeply, or from a purely scientific point of view, I would 

 trust to the intelligence of my fel^uw members of this 

 Association, to always kcLp the laws of nature so far in 

 view as not to go against them, otherwise the common 

 punishment of failure may and is certain to result, even 

 iu the construction of a chimney, when dealing with 

 heated air. 



The conditions necessary to secure control of the 

 movements of heated air, in, say, a common fire-place, are, 

 first, a supply of atmospheric air sufficient to furnish 

 oxygen for camhuftion, and a flue or channel of prcpcr 

 capacity to contain and carry off the expanded gases, 

 products of the combustion. To sect re the movement 

 of these gases in one direction, a difference i f level 

 is necessary nunc or less according to circum- 

 stances. This arises from the law that heat ex- 

 pands all gases, but they do not naturally rise— only do 

 so from the mechanical pressure of the atmospheric air 

 being greater below than above. The slightest difference 

 of level or pressure is sufticient to determine the movc- 

 meuts of a volume of heated gases or air, and, unfor. 



tunately, this is often painfully e.Nperienced in the heating 

 of large buildings, churches, theatres, etc, where numbers 

 of the audience are in one part of the house, being half- 

 sufiocateil with beat, othr IS in auolher part are starving iu 

 chilly draughts. This will always be the case iu such structures 

 more or less. Ssow there is a lesson for us in this — bow to 

 construct drying apparatus. We are thus led to deal with 

 small quantitiis of he:it(d air, or in other words to use it 

 in as small spaces as possible to gain economic effect. A 

 perfect drying machiue should have little waste space. The 

 whole of the heated or dried air should just have room 

 enough to play freely through and around the materials to 

 be dried, till its drying powers are exhausted. 



Here I wonUl direct your attention to the "Sirocco" 

 tea drier, not as an economical machine for substances 

 that may be dried slowly (of course a brisk heat is here re- 

 quired to check fermentation in the teaat a certain point), 

 but the principle of the cousti'uction of this drier is beauti- 

 ful anti simple. The hotter the fire the stronger the cur- 

 rent of heated air rises, this being suppiied from the 

 ordinary" open air of low temperature. Comparatively the 

 apparatus is thus nearly self-regulating, at all events safely 

 workable and admirably adapted for the purpose. It is 

 just on the same plan as one of the best modes of house 

 ventilation in use iu cold countries, where an apert- 

 ure is made into the flue at the highest point of a room 

 to carry off the overheated and vitiated air. 



The " Sirocco " is perhaps a model of a self-acting drier, 

 for certain purposes. The principle of construction is 

 correct. l.,et us consider how far the laws embodied 

 in the construction of the " Sirocco " can be availed 

 of in the work of drying such substances as cinchona 

 bark, or those which may be dried slowly and not 

 requiring any particular temperature. "Well, I have for the 

 la.st year or two used a drying-house, constructed on the 

 same lines as the " Sirocco." It works well, and a large 

 quantity of bark has boon dried in it in the wettest weather, 

 hut at a gieat sacrifice of fuel. The construction is 

 simply this. A furnace with brick horizontal Hues with air 

 drams alongside occupy ihe Boor, and so a current of heated 

 air is maintained to carry off the moisture in the bark, 

 resulting in the complete drying of the article. It works 

 well but as noted before not profitably, although, indeed, 

 it is a great improvement cu hot plates nr other im- 

 pervious material, which only dry by radiating heat. 



You will ob.serve at once, that in the case of the 

 Sirocco, or the drying-house just described, it is a ques- 

 tion of temperatuifc, whether circulation is kept up at 

 any given ))oint or at all. and that when it is maintained 

 it is at a loss of heat. So this being the case we are 

 driven back to the old '• Clerihew " idea, a beautiful one 

 in all resp(;cts, if properly carried out. It consists essenti- 

 ally of the providing of a discbarge of heated air into 

 the material to be dried, and the forcible removal of the 

 air after it has done its duty, by the use of fans, or 

 other mechanical appliances. 1 have seen but few of these 

 " Clerihews " at work, but lots of remains of them. The 

 idea is faultles.s, but the construction seems to have been 

 improperly carried out. It consisted of a large square 

 furnace, with a perpendicular chimney at one end of the 

 drying-house, aud the suction fans at the other. The 

 furn.ice contained a battery of cast-iron pipes to heat the 

 air disch:iv;jing into the house. The discharge or volume of 

 heated air would thus flow at a rate in proportion to the 

 partial vacuum caused by the fans. 



So far good, but the fault lay in the upright chiniuey, 

 which caused a great loss of fuel, the pipes taking out 

 a frafitiou of the heat available in the furnace. Now, 

 we purpose to improve on this particular, keeping always 

 hoKl of *hc beautiful original idea, not inventing but 

 adapting. "We know that if properly constructed a flue 

 for heating purposes may bo laiil nearly hirizomal, for 

 a loug distance. Now let this be dom-, for a bark dry- 

 ing-house, keeping *' Clerihew " fans ; let the air be 

 heated and dried by |>layiiig over the I'm nace, and along 

 the sides of a series of flues, so that all the heat may 

 be ahstracte<l, and you have a perfect drying-bouse, the 

 only lost heat being that rcqnireti to keei:i up tht! draught 

 in the chimney, which need be very little. The mechan- 

 ical force used in the removal of the stesmy air; is 

 equivalent to so much fnej saved as compared to the 

 " Sirocco " plan, while the management of temperature 



