Page:Popular Science Monthly Volume 24.djvu/67

Rh, say, fifteen feet a century at one end and a little over two feet a century at the other. This might be at the following rate, taking each figure for the growth of a century: 15 $$+$$ 13 $$+$$ 10 $$+$$ 8 $$+$$ 6 $$+$$ 3 $$+$$ 2 $$=$$ 57. By which calculation seven centuries would have been the tree's age when Sir Robert Atkyns declared it to be fifty-seven feet in 1712, an antiquity that would amply satisfy tradition, but could not remove the probability that the tree is not a single trunk, but really a number of different trees that have become incorporated together.

A somewhat similar theory may be applied to the famous Castagna di Cento Cavalli on Mount Etna, so called because a Queen of Aragon and one hundred followers on horseback are said to have taken shelter beneath it from a shower of rain. Brydone, in 1790, measured the circumference to be two hundred and four feet, but it seemed to him that the tree in question, of which only separate trunks remain, was really five separate trees; and though he professed to have found no bark on the insides of the stumps nor on the sides opposite to one another, yet a more recent traveler states, in Murray's guide-book, that this is only true of the southernmost stem, and that one of the masses still standing does show bark all round it, which would of course prove it to be a separate tree. Of the other large chestnuts on Etna the Castagna del Nave is rather larger than the Tortworth specimen, while the Castagna della Galea is seventy-six feet at two feet from the ground. The rich soil of pulverized volcanic ash combined with decomposed vegetable matter probably enabled them to attain their present size within a shorter period than would be implied by such dimensions elsewhere; but whether they are five centuries or ten it is absolutely impossible to conjecture.

The great variability in the rate of growth in trees of the same species is perhaps the most remarkable thing afforded by statistics. We say, for instance, roughly, that the beech grows twice as fast as an oak; but take four beeches mentioned by Loudon, placing their years in one column and their circumference in another:

So that of three beeches nearly the same in size one was only sixty, another one hundred and two, and another as much as two hundred. And this variability of rate is still more conspicuous in the oak. De Candolle, who counted the rings of several oaks that had been felled, found one that at two hundred years had only the same circumference that another had attained at fifty. Some had grown slowly at first, and then rapidly; others, like bad racers, had begun fast and ended slowly. And even the diminished rate of growth would not seem to be an invariable rule, for one oak of three hundred and thirty-three years was shown to have increased as much between three hundred