72 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
The crops in which these measurements were made were 
at the time (1goo) so thin, that further thinning would hardly 
be likely to stimulate their rate of growth to any perceptible 
amount. And, of course, this means that the trees will therefore 
take at least as long to increase by the next 6 inches in 
girth, measured at breast-height (1 inch radius = 632 inches girth), 
as the above measurements prove them to have taken for their 
last increase of 6 inches. The reader can easily tabulate for 
himself, should he desire to do so, the rate of growth for each 
individual kind of tree, according to the quality of the soil 
and situation in the various compartments. 
