460 TKAXSACTIOXS AND PKOCEEDIXGS OF THE [Sess. i.vii. 



of the rate of girtb-iucrease in such a tree till it attained, 

 say, 15 feet in girth, by using the data already referred 

 to, but we probably have none to help us for the period 

 during which the girth increased to 20 or 30 feet. The 

 only mode which appears to offer itself in such cases is to 

 ascertain the recent rate of girth-increase, and to allow 

 for a gradual diminution in the rate from that of the 

 calculated period at, say, 1 5 feet, to the ascertained rate 

 at, say, 20 or 30 feet. But it may be said that the rate 

 varies so much in the recorded data as almost to nullify 

 this system. I believe, however, that we are not likely 

 to err, if we take the quickest growers for our models, 

 as my experience in tree-measuring goes far to prove that 

 quick growth goes along with vigour, and I also found in 

 connection with the great frosts of 1879-80-81 that the 

 quick-growing trees of each species suffered least. 



We have still to consider the modes of ascertaining 

 the present or recent rate of girth-increase. The most 

 accurate and ready means is by using borers to extract 

 cylinders of • wood on which the annual rings can be 

 counted. Mr. J. E. Bowman* was the first to adopt this 

 simple method, but it was unaccountably neglected at the 

 time, and it was left to the German foresters to revive or 

 rediscover it in recent years. Mr. Bowman's borer pene- 

 trated only to a depth of a few inches, but cylinders can 

 now be extracted to a much greater depth, and, if taken at 

 several points at the same level, yield most valuable and 

 reliable results. But altliough no harm is done to the 

 trees by this instrument, permission to use it is not likely 

 to be granted by the owners of interesting old trees, and 

 the only remaining plan is the tedious one of taking girth 

 measurements for sevei'al successive years. This plan has 

 one advantaf'e over boring, as it shows whether the stem 

 is still continuing to grow, and it is eligible enougli in 

 trees of very great size which retain their health and 

 vigour. 



But in gnarled, " bumpy," and particularly in decaying 

 stems, neither by this nor by any other means can we 

 hope to arrive at any satisfactory result. The chief 

 difficulties in estimating the age of such decaying veterans 



* Ann. of Xat. Hist., 1837, i., X.S., j.. 28. 



