1834.] on the Longevity of Trees. 199 



1st. They would establish for each species an average of its annual increase, so 

 that by knowing the circumference of an exogenous tree, its age might be also pretty 

 accurately ascertained. It must be kept in remembrance that great variations take 

 place during the first period, and that afterwards a more uniform growth is estab- 

 lished. 



2ndly. The mean growth and mean solidity of any species of wood being given, the 

 thickness of the layers of an individual specimen will enable us to judge, whether it 

 possesses all the natural qualities belonging to its species ; thus it may be inferred, 

 that the oak No. 1 of the table, is very inferior to the oaks 2 and 3, because the 

 thickness of the layer is too great for the wood to have acquired its full hardness. 



3dly. If the law I have assumed is true, that at a certain age (60 or 80 years 

 for oaks) every tree ceases its more rapid growth, and assumes a more regular pro- 

 gress, then we may deduce precise rules as to the most suitable period for cutting down 

 certain trees. I am inclined to believe, therefore, that tables of horizontal cuts 

 would be of very great use, and I recommend their preparation as well to travel- 

 lers as to those engaged in extensive timber-works and building concerns. 



2. When the transverse section of the stump cannot be obtained, a second 

 method presents itself, by which the growth may be determined ; which is, to look 

 for the old individuals of every species of which the date is ascertained, to measure 

 their circumference, to deduce from thence their average growth, and to make use 

 of this to calculate the age of other trees of the same species ; bearing in mind, 

 that, except in local circumstances, a measure taken from a young tree always pro- 

 duces too great a result for the growth, and too small a one for the age, of old trees. 

 Evelyn mentions, that a Dane, named Henri Ranjovius, planted in Ditmarches, in 

 the year 1580, a certain number of trees of various kinds ; that he placed near each a 

 stone recording its date, that posterity might know their age. It would be very 

 interesting to ascertain, whether these trees are still in existence, and if so, to know 

 their circumference ; in fact, it would be interesting to have the circumference of 

 every ancient tree the origin of which is known. I invite all who have such par- 

 ticulars, either to publish them, or to communicate them to me ; for such obser- 

 vations can only prove useful by comparing them with other recorded facts. 



3. For trees of slow growth (s^culaires), it is useful to have their circumferences 

 at different known periods, so that they may be compared one with another, or with 

 other measures of the same tree which may be taken sooner or later ; these compa- 

 risons would afford means for better calculating the law of growth, and of appreciat- 

 ing the influence of differences in age ; thus, for example, the cedar in the 

 garden at Paris, which was measured when 83 years old, was 113 inches in circum- 

 ference, which would indicate an average of nearly 0.44 in. growth in the year, 

 but it was measured when 40 years old, and had then already 84 in. cir- 

 cumference ; from which it seems that it grew 0.66 in. a year during the first 

 40 years, and only 0.23 during the following 43 years : consequently if the age of a 

 very old cedar were required to be calculated, we should not probably go far wrong 

 in taking this last number as a multiplier ; thus the cedars at Liban measured in 

 1660, by Maunorell and Pocock, which were 12 yards and six English inches in 

 circumference, must have been about 609 years old ; and in 1787 when they were 

 again measured by Mr. Labillardiere, about 800 years. But the calculation is 

 doubtful since it only rests upon a single example : it would become more certain 

 in proportion as the number of instances becomes greater. 



4. It would moreover be useful to take the circumference of very old trees, 

 whenever met with, even when their date is not known. These measures repeated 



