1st tree. From 1780-1889, an increase from 6´ 3´´ to 9´ 10´´; a gain of 3´ 7´´. 2nd “ From 1834-1889, an increase from 9´ 2½´´ to 9´ 6´´; a gain of 3½´´. Now, if it be true, as Dr Lowe’s rule supposes, that a mean period of 65 years represents a gain of one foot in diameter, the first tree should have increased 5´ 3´´ in circumference, and the second 2´ 8´´. But here, again, the postulated rate of growth is far too high; in the second example, nine times too high. Even if we grant that “old trees grow, at intervals, much more rapidly than young ones,” Dr Lowe’s main rule is not verified. For it happens that measurements of the first tree were made at two intermediate dates, 1796 and 1834. During the first period, 1780-1796, the increase was indeed three times as great as Dr Lowe’s formula would demand, but in the second, and longer period, 1796-1889, the growth was less than a quarter of the estimated amount. These measurements of yews, dealing with odd inches, truly suggest some degree of error, due to the substitution of one observer for another, nevertheless, we may assume the figures to be roughly correct. At the same time, these rather surprising results indicate the wisdom of calling in the aid of the total ring-estimate as a supplementary witness, since the increase of girth tends to be so variable. Particulars respecting the growth of yews at Wrexham, as given by John Timbs, also show that an increase of one foot in 65 years is somewhat over the limit[965]. More records are desirable, yet the facts generally seem to favour Dr Lowe’s higher limit of 70 years for each foot of growth, or even the 75 years proposed by the Christisons. On the whole, Dr Lowe himself seems to sanction the last-named estimate, for, while he thinks that one foot in 75 years is “below the average rate of growth,” yet for purposes of calculation he prefers to adopt that scale[966]. The basis of 75 years, then, shall be taken in the present chapter. Two reservations, dependent upon what has been said previously, must, however, be borne in mind. First, seeing that young trees have, proportionately, a more extended leaf surface than old ones, larger rings are formed and the 75-years rule will make the trees too old. Secondly, and more important, there seems to come a period when aged trees are practically at a standstill; they make no more increase, but linger until disease and decay set in and slowly drain off the vitality. Of the yew at Aldworth, Berkshire, it is asserted that it has not increased in circumference since 1760[967]. I feel sure that this arrest, though not usually absolute, is very common; hence, for aged trees, additions to the age must be made after applying the 75-years rule. Much stress should be laid on this point.