THE DOUGLAS FIR PLANTATION AT TAYMOUNT. 275 



the seed was sown (1856), we have a mean height-growth of TTT 

 feet per annum, and a mean annual increase in volume per acre 

 of 238 cubic feet. 



The contents of the two sample trees are calculated both as 

 to true contents and also by the English system of quarter-girth 

 measure. In the case of No. 1, the true volume was 58"93 cubic 

 feet, while the quarter-girth contents were 4:6-76 cubic feet, so that, 

 to reduce the former to the latter, it is necessary to deduct 20 "65 

 per cent.; while to convert quai-ter-girth measure into true 

 contents it is necessary to add 26 "03 per cent. 



In the case of tree No. 2, the corresponding percentages are 

 21-4:1 and 27*25. For ordijiary purposes, therefore, it will 

 suffice to add a fourth in converting quarter-girth contents into 

 continental or calliper measure ; while to convert the latter into 

 the former a fifth must be deducted. Dr Schlich's sample tree 

 contained about 14 cubic feet quarter-girth measure, so that an 

 acre carried — 



14 X 202 = 2828 cubic feet. 



The smaller of the sample trees measured this year contained 

 39 '49 cubic feet by the same system of measurement, therefore — 



39*49 X 202 — 7977 cubic feet per acre. 



In 1888 Dr Schlich calculated the "form figure" of the Douglas 

 fir, at the age of thirty-two years, to be '39, and anticipated that 

 it would gradually decline.^ This, however, has not proved to 

 be the case, for, in the case of sample tree No. 1, the form figure 

 works out at — 



Volume 58-93x12x12x12 ,,, 



= -441, 



Sectional area x height 240-53 x 80 x 12 

 while in the case of No. 2 it is 



50-25x12x12x12 ,,^ 

 •456. 



191-13x83x12 



If the less favourable of these form figures, namely, -441, be 

 used to calculate the true timber contents from the mean of the 

 two sample areas, we get — 



295 X 80 X -441 = 10,407 cubic feet, 

 ^ Loc. cit., p. 237. 



