RUBBER 643 



inclined cuts to the right at the same height, whether 

 on the same or opposite sides of the tree. 



(4) A yield from a V cut is greater than that from a 

 single cut to the right whose length is equal to the com- 

 bined length of the two arms of the V, but less than the 

 yield of a similar single cut to the left. 



The first two results, though some exceptions were met 

 with, establish the general rule that it is immaterial on 

 which side of the tree a tapping experiment is instituted. 

 The third and fourth are of great importance in actual 

 estate tapping. It may be explained that the phrase 

 " tapping to the left " has been adopted to denote the 

 half herring-bone system with the cuts to the left of the 

 vertical channel. 



We may now proceed with the special object of this 

 paper, which is to discuss the results arrived at in various 

 tapping experiments and the practices generally adopted, 

 from more or less accurate results, on estates. It will 

 be convenient to consider them under the different factors 

 which are now known to influence such results. 



The Area of the Tapping Surface. 



By tapping surface is meant the part of the tree which 

 is being tapped on any one occasion. Area of tapping 

 surface is usually stated, as far as its breadth is con- 

 cerned, in terms of the circumference. The tree may 

 be tapped all round, or on a vertical strip whose breadth 

 is one-half, or one-third, or one-quarter of the circum- 

 ference. 



Tapping all round the tree at the same time has been 

 abandoned, though an approach to it still exists in some 

 " change over " systems. Excision systems which tapped 

 all round the tree were the full spiral, and the full or 

 half herring-bone on both halves of the tree, tapped on 

 the same day. An experiment carried out on young trees 

 at Peradeniya showed that, in alternate day tapping for 

 a year, the full spiral, tapping all round the tree, yielded 

 less than either the full or the half herring-bone on half 

 the tree. The experiment is not free from objection, but 

 the difference was so great that it is probably correct. 



