Page:Timber and Timber Trees, Native and Foreign.djvu/36

16 that the largest he measured of this species was about 36 feet in diameter.

Decandolle gives the following list of the ascertained ages of the undermentioned species of trees:—

These figures have, doubtless, been based and computed upon the supposition I have advanced of there being one concentric circle for each year of growth; but, as they do not serve us for any practical purpose, we must look to those trees of moderate dimensions, which attain to maturity in a shorter time, rather than to those I have enumerated, for the timber we may wish to employ for architectural works. The record, however, which these circles afford of the duration of life in trees possesses a value of which we cannot but feel the importance.

I have carefully examined and counted the annual layers of a great many specimens—taking generally an average of ten trees—with the view to show the common and comparative rates of growth, and have tabulated them to afford an opportunity of noticing any variations there may have been in the time required to form the wood in each of the several given diameters of 6, 12, 18 inches, &c. This evidence of the ordinary rate of growth, and the time which it takes to bring the various descriptions of timber trees to maturity, will be of value to us when considered in connection with the properties and characteristics of the timber employed for architectural works.

The number of concentric circles, or woody layers, found in various timber trees, within a radius of 3, 6, 9,