64 RUBBER AND 



those of Parkin more closely. It must be remembered 

 also that the method of tapping employed was entirely 

 different from that of Parkin, who used an incision 

 method pure and simple, and did not reopen the same 

 wounds. The result of all such experiments may be 

 summarised as follows. With any moderate method of 

 tapping, carried out at nearly equal intervals, which 

 may vary in length from 24 hours up to 10 days, the 

 yield per tapping rises rapidly to a point at which it is 

 subsequently maintained, subject to certain variations 

 the nature of which will be considered later on. 



Duration of yield. 



With moderate and careful tapping no limit can at 

 present be set to the period during which a similar yield 

 will continue to be obtained from Hevea. By the end 

 of April 1912, the tapping of the same seventy trees 

 had been continued without intermission for nearly four 

 years. The annual yields obtained are summarised in 

 the following table: 



TABLE XII 



Yields calculated to Ibs. of dry rubber per acre. 



Row 



Year I. II. III. IV. V. VI. VII. 



1908 (7 months)... 950 590 485 390 335 345 240 



1909 ... 890 600 480 380 360 340 265 



1910 ... 900 540 380 380 370 300 255 



1911 ... (350 1 ) 700 500 620 580 500 370 



1912 (4 months)... 180 145 220 240 220 165 

 Average annual 



yield for 4 years ... 770 650 500 500 470 425 325 



1 For 4 months. 



