THE GIRTH-INCREASE OF TREES. 73 
girth, had a rate of '57, while one at Craigiehall, six and a half 
feet in girth, gave a rate of ‘92 for eight years, and a very 
vigorous specimen at Cramond, nearly thirteen feet in girth 
when measured in 1878, must certainly have been a rapid grower. 
The handsome Sycamore, No. 28, five feet in girth, with the 
unaccountably low rate of -35, is not much above the ‘22 of the 
largest Sycamore, eleven feet in girth, in the Garden; and a 
Craigiehall tree, nearly as large, excelled it with a rate of ‘40 for 
ten years, 
The finest Birch in the Garden ceased to increase when a few 
inches short of five feet in girth, while a slightly larger specimen 
at Craigiehall continued to grow at the rate of nearly half an 
inch for eight years. 
D. Aggregate Annual Results. 
The results in the aggregate are chiefly interesting as showing, 
in the first place, the effects upon girth-increase of good or bad 
seasons ; and, secondly, any tendency there may be towards altera- 
tion in the rate from increasing age in the trees. This inquiry 
must be confined to the group of adult and aged trees, as in 
them alone has the period of observation, amounting in most of 
them to twenty years, been sufficient to yield reliable results. 
As the two kinds of results just specified are concurrent it will 
be easier to study them together than separately, and it will be 
advantageous to take first the species which seem to be still 
growing with undiminished vigour, as far as external appearance 
goes, and subsequently those that may be suspected of having 
decidedly passed their prime. The first set includes Beech, 
Hungary Oak, and Turkey Oak, of each of which from two to 
four specimens were under observation. These will be dealt 
with separately. The second set contains nine species, mostly 
illustrated by only one specimen, and may be taken in mass. 
The first decade of observations, 1878-1887, was remarkable 
for three successive most unfavourable seasons, 1879, 1880, and 
1881. In all three the winters were marked by exceedingly low 
temperatures, and in 1879 the growing months were remarkably 
cold and sunless. Fortunately the measurements in most of the 
species began in the previous year, and thus we can appreciate 
the extraordinary immediate loss in the aggregate girth-increase 
¢ 
