166 THE RUBBER TREE BOOK 



Expressed as percentages of the average yields for 1909-10 

 the increases are as follows: 



II. HI. IV. V. VI. VII. 



17 29 59 55 56 38 



" In view of the figures for January and February, 1912, 

 the conclusion presents itself that we are rapidly approaching 

 a period when the crop gathered once a week will exceed the 

 crop gathered every three or four days. According to the 

 figures so far available, an interval of six and a half days 

 (Row V.) appears likely to give the best final result. All the 

 tables here given show a distinct falling off in the case of Row 

 VII., indicating, as might have been expected, that nine days 

 is too long an interval. The best yield per tapping is given 

 throughout by Row VI., and the best total yield for January 

 and February, 1912, by Row V. To revert to the subject of 

 the early part of this article, if these were the only facts available 

 we should be justified in recommending a period of renewal of 

 eight years as superior to one of four years." 



The results have since been confirmed by continued 

 tapping experiments. 



As has been already stated, although the foregoing methods 

 of tapping are very dissimilar to the single half-spiral cut re- 

 commended in this chapter and to the broad V cuts experi- 

 mented on by Mr Skinner, yet while all of them are very sparing 

 of the bark, the returns of latex are in excess of those obtained 

 by ordinary tapping methods. 



If further proof were needed to establish the fact that as 

 good or, as is contended, greatly better yields of latex can be 

 obtained by making less than half the number of cuts so com- 

 monly employed, it can be very readily forthcoming. 



The best yield per acre on any estate in the East, so far as 

 is known to the writer, namely, over 1200 Ibs. per annum, is 

 obtained on the well-known Pangkattan Estate, Sumatra, be- 

 longing to the Sumatra Para Rubber Company. This extra- 

 ordinary yield is obtained from only three cuts on the half- 

 herring-bone quarter-section system. These three cuts in- 

 volve the paring away of rather more bark than would be 

 cut away by the two right and left-hand cuts to form the 

 broad V adopted by Mr Skinner or than would be shaved 



