Correspondence. 



262 



[Sept. 1906. 



At A. erect A. C. and at B. erect B. D. pependiculars 5 inches. Join C. D. 



A. C. D. B. is the tapping area for the spiral. 



Bisect A. B. at E. and raise per pendicular to F. ; E. F. D. B. is the tapping 

 area for half-spiral and herring-bone. 



Divide these perpendiculars into foot lengths. From E. draw E. G. at 45°, to 

 1 foot above B., and parallel to this draw the rest of the lines from the 1 foot 

 spacing points. These are the half-spiral channels, F. E. is the runnel. A glance 

 shows that above the topmost channel is a triangle of untapped bark whose 

 base is F. D., and below the lowest channel is a triangle whose cuts gradually run 

 out, away from the runnel and disappear at B. 



For the herring-bone bisect E. B. at H, run a perpendicular up till it meets 

 the top channel at I. H. I. is the runnel. Join I. F. I. D. I. F. are the top channels. 

 Parallel to I. F. from the one foot points draw the other four lines to the central 

 runnel. At the top a triangle F. I. D. is left untapped, and it will be seen that, when 

 the lowest channel reaches the foot of the runnel, two small triangles will be left, 

 the cuts on which will gradually run out at E. and B. 



Comparing these two systems, it will be seen that— with its disability of loss 

 of tapping area — the half-spiral requires, after the cut has begun to run out at the 

 bottom, only one extra spout and collecting cup to the herring-bone's extra two, and 

 only five applications of water, or five drip-tins to the herring-bone's ten ! 



Even pretty Karrupaie, deftly watering the cuts from a sort of bitters-bottle 

 and buzzing around from tree to tree in her little group of five or six trees at a time, 

 would prove far too expensive a luxury, however picturesque ; so let us hasten to 

 the spiral. 



For the spiral : from A. draw A. K. at 45°, i.e., to the 2nd foot spacing above 



B. This line has completely encircled the tree, so go level across the figure from K. 

 to its coinciding point K2, draw K2 L. at 45°, go across again to L2 and draw L2 Y. 

 at 45°. The spiral has reached the top of the tapping area and encircled the tree 

 two-and-a-half times, and as will be seen at a glance is of precisely the same length, 

 viz., 84 inches (7 inches on the scale) as the sum of the lines in each of the other two 

 systems. It requires one drip tin, one spout, and one collecting vessel ; cut after 

 cut will be the same all round the tree, there is no untapped or untappable area. 

 Nay, more than that ; it will reach further down any inequality of root or base of 

 the stem even where the others cannot go. Further, it is seen that the spacing is 

 two feet, so that an intermediate channel cculd be put in, but this would finish the 

 bark in half the time. But if — as seems to be the idea just now with the improve- 

 ments of modern paring and pricking —one foot is held to be enough bark to go over, 

 in the time it requires for the originally cut bark to have grown thick enough 

 again, to cut a new channel in and start over again, its superiority is at once assured. 

 The two spirals, being at all times on opposite sides of the tree, the yield is at each 

 time, early or late, at any period, monsoon or fine, in any aspect, to the dark side or 

 the open, an averaje of the productivity of the tree for the time being, which 

 is more than can be said of the other two, or of " compass tapping." 



All this is of spiral tapping on the angle of 45°. What of the lower tapping 

 angles of 30° or 35° which are now available through the use of water, which will go 

 a few more times round the tree and give a much larger yield ? On suitably large 

 trees, say 36 inches in average girth, they will enable the planter to tap a large 

 and fertile area at the base of his tree, say only 3 ft. 6 in. or 4 ft. up, and then 

 with a low platform to tap a second story, the top of whicn need only be 

 8 ft. up, if this procedure is found to be necessary, which some men maintain 

 is the case. 



