Sept. 1906.] 



261 



C orrespondence. 



Those who have followed the argument will see that it is manifestly unfair 

 to compare tapping done on flat angles with that at 45°, in which latter the channel 

 has to be probably 25 per cent, longer, in order to cut across the same number of 

 cells, and therefore, with greater waste of bark— the paring being the same in 

 thickness in both cases. And it was just at this point, unavoidable though it may 

 have been, that the flaw occurred and the deduction was wrongly drawn as to the 

 merits of these two systems. Given the same angle, I maintain that the spiral will 

 beat the herring-bone in yield per unit of bark excised ; for it can easily tap all the 

 basal portions of the tree, where the latex is in greater quantity and richness, which 

 are only reached by the herring-bone and half-spiral with difficulty and inconveni- 

 ence, owing to their peculiar construction. 



And with the advent of water flotation 

 and the drip-tin especially — which is an 

 unalloyed blessing in its prevention of 

 scrap and of manual labour, watering the 

 cuts — the necessity to tap at 45° for the 

 spiral has disappeared, and a much 

 smaller angle, say 30° or 35°, can be taken. 

 This will be a matter for experiment to 

 those interested. 



At any rate, the day is passing aAvay 

 when the practical planter will tolerate 

 the expenditure of attendants watering 

 the cuts by hand when it can be done by 

 mechanical means. 



It stands to reason then that, at what- 

 ever angle a herring-bone can be cut for 

 self-acting water flotation, at that angle 

 also can the spiral be cut, and also the 

 half-spiral which, however, exceeds the 

 herring-bone in amount of untappable 

 and inconveniently tappable areas. These 

 amount to, at least, one-fifth of the 

 whole in the half-spiral and one-tenth 

 of the whole in the herring-bone, as 

 compared with what can be done on 

 the spiral method within the reach of 

 the average tapping cooly — that is, five 

 feet. 



" Perhaps a sketch, which any one can 

 easily make for himself, will not be out 

 of place here. Let us take the case of a 

 tree averaging 24 inches in girth (never 

 mind the tapering shape, for it affects 

 all three systems in the same way) the 

 tapping area as five feet above the level 

 of collecting vessel, and the spacing as 

 one foot, and the scale as one inch to a 

 foot. 



Draw the line A. B. =two inches. 



