1 6 TIMBER AND TIMBER TREES. [CHAP. 



tions 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 : 



Elm . ... 



Cypress 

 Larch . 

 Cedar . 



These figures have, doubtless, been based and com- 

 puted 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, 1 8 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, 



