LETTER II. 



17 



trunk on a level with the ground ; or, having ascer- 

 tained the average rate of growth, to deduce the age 

 from the thickness of the trees. This method, it may 

 be observed, is applicable only to exogenous trees, 

 and even as regards these is beset with certain fal- 

 lacies, although on the whole, and for general pur- 

 poses, it is sufficiently accurate. Subjoined is a table, 

 drawn up by himself and others, of the ages of cer- 

 tain trees : — 



Elm, . 



355 years. 



Cypress, 



350 ... 



Cheirostemon, 



400 ... 



Ivy, . 



450 ... 



Larch, 



576 ... 



Chesnut, 



600 ... 



Orange, 



630 ... 



Olive, . 



700 ... 



Oriental Plane, 



720 ... 



Cedar, 



800 ... 



Lime, . 



1076, 1147 ... 



Oak, . 



. 810, 1080, 1500 ... 



Yew, . 



1214, 1458, 2588, 2880 ... 



Taxodium, 



3000 or 4000 ... 



Boabab, 



5000 or 6000 ... 



Dracaena, 



6000 ... 



9. Now, what is the real import of this table ? What 

 the precise value, in relation to our present inquiry^ 

 of the data suppHed by De Candole for estimating the 

 age of trees ? What we want to know is, the natural 

 longevity and the natural size of trees — their average 



