-9' 'JTI1-: I'.LACK WATTf.l-: IXnrSTKV. 



\\ ider espacenient also tends to carry mature and heavv 

 bark further up the tree, and to increase its proportion per acre 

 in that way. 



Wilhams made further experiments com])arinty bark dried 

 in the open air with other portions of the same sample dried 

 in an oven at a temperature approximating to 60° C. (or 

 140° F.) These agreed so closely that up to 150° F. is con- 

 sidered safe against damage or loss, especially if accompanied 

 by thorough ventilation to dry ([uicklv without destruction of 

 tanning matter. 



This may eventually be useful toward the coast, where the 

 humidit}- of the atmosphere often makes successful drying diffi- 

 cult. All these experiments by Mr. Williams were duplicated 

 the following winter, and proved that summer and winter 

 felling give practically equal results, and that the first experi- 

 ments were confirmed throughout. This was issued bv ( lovern- 

 ment in ]iamphlet form as No. yi, 191 5. 



I ha\e only casually referred to what bark constitutes a 

 crop. Of course, this varies immensel}- in accordance with con- 

 ditions and cultur^. 



But, allowing average suitable conditions, the usual weight 

 of dry bark obtained is from half a ton to a ton per acre during 

 thinnings, which hardly do more than i)ay exjKMises, and about 

 three tons per acre final crop in a 6-year rotation, or four tons in 

 an (S-year rotation, if no pests or troubles have interfered. 



I'hat is to say, apart from the unremunerative thinnings, 

 half a ton per year per acre of bark increment is a good crop up 

 till tlie eighth year, and very many indeed an- the crops which are 

 not up to this standard meantime. 



We have no sufficient data on which to base calcitlations of 

 further increment, but if thinnings have been satisfactorily done 

 and conditions are favourable, 1 estimate the increase after the 

 eighth year at three-(|tiarters of a ton per acre for several years, 

 and ])robal)ly often more. 



Meantime we do not have reliable data on wliicli to base yield 

 tables or _\ield curves, but the necessit}' for these is urgent, and 

 I stiggest that Government take the ])reparation of such tables or 

 cm-ves in hand at once. 



The farmer or the conipan\- is only interested in his or its 

 own cro]); it is a (iovernnient dut}- to compile such tables, appli- 

 cal)le to all cases. 



An erroneous idea is common that wattle, in ad<h'tion to 

 drying out the local soil, has a drying eff'ect u])on the district 

 generall}-. In Bulletin No. 7, 1905. I wrote: — 



" A plantation of mature black wattle transpires regularlv an 

 amount of moisture ecjual to about 40 inches of rainfall under the 

 ordinary temperatures of Natal Midlands. conse((uenth-. if the 

 su])])ly of moisture from all sources is less than that, the planta- 

 tion will eventually dry out the ground and suff'er ; whereas, if the 



