110 On the Longevity of Trees ^'c. 



Henry Ranjovius, planted a certain numter of trees in loSO, in 

 Ditmaisen, of various kinds, and placed stones near them, on 

 which he engraved their dates, that posterity, as he said, might 

 be aware of their age. It would be curious to know whether 

 these trees are still in existence, and, in such a case, to get their 

 circumference. It is a question that I address to Danes who 

 are fond of science, and, in general, it would be curious to have 

 the circumstance of every tree whose date is known, and is up- 

 wards of a century old. I would even venture to invite all those 

 who have similar documents, either to publish them, or to com- 

 municate them to me, as these facts arc very useful by their 

 comparison with others. 



3. As to trees 100 years old, it is useful to get their circum- 

 ference at various known periods, in order to compare tliem 

 with each other, or with other measurements of the same tree, 

 which may have been made at an earlier or a later period. 

 These comparisons would afford means for a more accuiate cal- 

 culation of the law of the growth, and appreciating the influ- 

 ence of the difference of a-e. Thus the cedar, in the Jardin de 

 Paris, for example, measured when eighty-three years old, 

 was 106 inches in circumference, which would indicate a mean 

 increase of five lines annually ; but it had been measured at the 

 age of forty years, and at that time was above 79 inches round. 

 We are thus aware that, during the first forty years, it increased 

 7|- lines ainmally, and only 22- for the succeeding forty-three ; 

 consequently, if we were going to calculate the age of a very 

 old cedar, we should not be very far wrong did we take the 

 latter as the multi])lier. Thus the cedars measured at Lebanon 

 in 1660 by Maundrel and Pococke, which were 12 yards and 

 6 inches round, English measure (it may be about 1527 lines in 

 diameter royal measure), should be about 609 years old, and 

 nearly 800 in 1787, when they were revisited by Mr. Labillar- 

 diere. This calculation is doubtful, however, as it is founded 

 on a single example ; it would be much more certain were the 

 number of examples increased. 



4. It would also be useful to take the circumference of some 

 very old trees which wc may meet, even though we are igiio- 

 rant of the time when they were planted. Such measurements 

 repeated at stated intervals, would inform us of the law of the 

 diametrical increase of old trunks, and, compared with other 

 measurements, would give approximate averages for estimating 

 their ages. Thus, in Evelyn, wc find, that in 1660 there was 

 an immense oak in Wellbcck Lane, which was 33 feet 1 inch 

 round, about 1 1 feet perhaps in diameter. The same oak, 

 though greatly mutilated, existed in 1775, and was 12 feet in 

 diameter ; of course, it had increased about 144 lines in 120 

 years, a little more than one line annually. From this wc may 



