1(J 



LtTTEKS ON TREES. 



the second, he says, in general terms, that certain 

 trees acquire, after many years, a considerable height 

 and thickness, and m particular, that the greatest 

 increase m height which the forest-trees of France 

 arrive at is from 120 to 130 feet — those of America, 

 however, often exceeding 150 feet. And in the third 

 section, he observes that the trunks of individual 

 Boababs have a girth of ninety feet ; the trunk of a 

 Dragon-tree in the Canaries, a girth of forty -five feet ; 

 that of a Sycamore in South Carolina, a circumference 

 of sixty-two feet ; and lastly, that in France certain 

 trees which he specifies have trunks with a girth of 

 from twenty-five to thirty feet. 



.8. We are still, I fear, as far off as ever from the 

 discovery of the laws which we are seeking to ascer- 

 tain. Let us turn next to M. De Candole, and inquire 

 of him what he knows on the subject. This eminent 

 botanist has written largely and very expressly on 

 the longevity of trees. All that I happen, however, 

 to know of his researches, is what is to be met with in 

 our Enghsh works on botany, and these merely give 

 us the result of his examination of certain trees, toge- 

 ther with details as to the method he followed in his 

 estimate of their age, and the data he supplied for 

 computing the rate of growth, and consequently the 

 age, of trees generally. His way of getting at their 

 age was to count the number of annual layers or rings 

 of wood — reckoning, of course, at that part of the 



