6sS 



THE TROPICAL AGRICULTURIST. 



[March i, 1884, 



The followinc' analysis of a virgin clay soil of 

 Demeraia (analysed by Dr. Phipson, see the Svgar- 

 cane for I)ec. 1879), and which may he taken as a 

 type of Demerara clay soils generallj-, may interest 

 you and your readers. 



Water ...24-18 ...97-32 



Organic matter ... 7'87 Phosphoric acid ... O-IO 

 Silic.'ite of Ammonia Sulphuric acid ... 008 



and Silica ...64-42 Chlorine ...0-05 



Lime ... 0-44 Oxide of iron, 1 



Magucsia ... 0-29 Alumina etc. ', 2-45 



Potash .and Soda ...0-12 (soluble iu HOI) ) 



97-32 



100 00 



—I am, yours faithfully, S. E. B. CURTIS. 



[It is curious that Mr. Curtis should have attributed 

 previous failure to deficiency of rainfall, while we 

 thought too great humidity was the real cause, in 

 preventing crystallization. — En.] 



IRON AND BRICK AS CONDUCTOES AND 

 DIFFUSERS OF HEAT. 



De.^r Sir,— Before replyingto Mr. Cameron's remarks 

 in defence of his "drier," it seems to me a special 

 tribute is due to his ijhil'Suphic spirit. It is not often 

 one sees such a calm and pliilosophic defence of a 

 great scheme ; also he is to be connnended for having 

 put tlie matter into a debateable form. 



The chief points on which Mr. Cameron differs 

 from the "Clerihew" plan are in the use of brick 

 rather tliau iron ; and drawing, with his fan, the air 

 itp, instead of down. 



The use of brick, instead of metal, for the Irans- 

 nussion of heat is contrary to all custom. The jiro- 

 blem is to transfer the heat from the fire, smoke, 

 etc., tlu-ough some medium that -will keep in tlie 

 smoke and only transmit the heat to the air outside 

 of it. 



Now, in practical works of all sorts, brick is used 

 because of its low diathermous quality to retain heat. 

 To prevent heat jjassing from their boilers to the 

 air outside, engineers cover them with l)riok. The 

 baker uses brick for his oven, because it returns the 

 heat inude, and does not let it out. Smelters of iron 

 use brick for their fui-naces ; and while the lieat inside 

 is far above the melting point of iroji, the outside 

 may be touched with the hand. 



Mr. Cameron very properly pu'.s the case as to 

 be tested by the temperature at whicli the fire-heat 

 leaves tlie heating flue for tiie chimney. 



He says :" By my design the loss of the iire-heat 

 is at drying-house temperature." Is it so '! or any- 

 thint; bke it? Suppose the outside of tho brick of 

 his Hue at the exit to the chimney be at drying- 

 house temperature, say 90°, what will the iiiKifle temp- 

 eraliii-e he. The exi^eriiiieut can easily be made, I 

 and, I think, I may safely say tliat, when the out- 

 side of the brick (that is, the side furthest from 

 the heat) is 00°, the inside will be far up iu the | 

 hundreds. For not only is brick's diathermous qualil-y, 

 when compnrfd with iron, as I to 30, but iho brick 

 is 3 or 4 inches compared to a half-iucli of iron, 

 which increases tho advantage of iron from .'-iO to 1 

 to 6x30 or 180 to J, supposing the ligurcs correct. 

 Tbo ne.\t point is " up or down. " If Mr. Cameron 

 will make the experiment of kindling a fire on the 

 Hoor of a large room, he will note that soon a cur- 

 rent is established of healed air, smoke, &-.. up- 

 wards. When the smoke reaches the rjof, it gels 

 cooled, by contact with the roof and iu other ways, 

 and begins gradually to spread out, filliug the room 

 from the roof downwa'ds. But it is not the heated 

 ail- from the fire that is kept lowest. The current 



of smoke from the fire goes continuously through the 

 heavier smoke to the roof, and occupies the space 

 next to it. If a hole be open'd in the roof, there 

 will be established a eurrent from the fire to it, 

 through among, the heavier smoke, the hotter and 

 lighter going first, and the heavier last. Now, what 

 is wanted is to remove the cold air that hai done 

 its work in di-yiug, and an esperimeut on smoke 

 will show that that cau be done most ctleotually by 

 driving away the coldest from below. 



Or, if Mr. Cameron tests his plan with a thermo- 

 meter, he will find that there is a current of the hot 

 air from the hottest part of his five taking the easiest 

 course to th^. fan, and the rest of his drying-room 

 is filled with comparatively cold and saturated air, 

 as the "wet and dry bulb" thermometer or other 

 hygrometer would show. 



Hoping I have not tresspassed on your space more 

 than the value of tlie question at issue deserves, 

 I remain, yours truly, ' J.- B. 



[The discussion is most interesting and valuable, 

 and has an immediate bearing on a question which 

 has been raised regarding economy of fuel in pro- 

 ducing heat iu tea-drieis. One of Jackson's iu use 

 on Abbotsford does ito work well, but the con- 

 sumption of wood fuel is equal to 4 lb. for 1 lb. of 

 dried tea, while it is claimed for other driers that 

 1 lb. of fuel will suffice for each pound of te:i. We 

 gather that the remedy iu the case of the -Jackson 

 lies ill a judicious use of brick, so as to couceutrate 

 the heat where it is specially wanted 'I — Ed.] 



MR. GRAHAM ANDERSON ON FUNGOID 



DISEASES AND ARTIFICIAL 



MANURES. 



Mysore, 24th January, 1884. 

 Dear Sir. — in a recent issue of your invaluable 

 Trojncal AgrkuhurUt you published a leHcr recom- 

 mending superphijsphate us a remedy for " rust " iu 

 sugarcaui>, and iu youi- not" you inquire if anyone, 

 has noticed a timiliir beneficial effect on coffee siiffer- 

 ing from leaf-dieease. 



Many months- aijo, I hail the pleasure to hand you 

 a memorandum of my humble couolusious in regard 

 to the effeut of certain mmiirial preparations con- 

 taining phosphates and alkalis, aud, in my letters 

 dated 10th iVlaroh ami 2Gth June ISSl, I ventured 

 to point out the widely dill'ci.eut results obtained 

 by the use of chlorides, nitrates and sulphates. 

 Subsequently, you were also kind, enough to publish 

 another letter of mine relative to the beuellts deriv- 

 able from the careful selection and change of seed. 



Tii-jse papers were supplementary to an essay which 

 I had wi-ittcu on fungoid dise.ase, in which I advanced 

 a theory, founded ou ohservations made on coffee for 

 several years past, that the pi-tsenco of food con- 

 genial to the life and requiremen's of the parasite 

 occurs during a peculiar tiausiloiy state of the starchy 

 and sugary constituents of the c>ill-sap arising iu all 

 probability friin a deliciency of alkalis aud phosphates 

 in an available condition in the soil. 



This essay was siibmitieJ by the Government of 

 Madras fur opinion and report to the Conservator of 

 Forests aud the Superinteudeat of the Govcrumeut 

 Central Museum. 



I naed soarcelv say that the view expressed by 

 the Con eivator of Forests on my humble suggestions 

 did not tend to stimulate me to proceed with my 

 investigations, but I was specially grateful for the 

 oucouragenient extended to me by the valued remarks 

 made by Surgeon-Major Bidie, c. S. i. 



After having read the Forest ConscrTator's report 

 and compared it with the result of the Goveruuiea 



