54 THE POPULAR SCIENCE MONTHLY. 



at the point of fracture that caries into the trunk which will ulti- 

 mately reduce it to a mere shell, similar to one of those bull-oaks 

 wherein the bull loves to hide himself. These causes of disease and 

 decay can never be absent, since they evidently belong to the perma- 

 nent order of nature. 



Again, De Candolle accounts with great probability for the di- 

 minished rate of tree-growth after a certain period by such considera- 

 tions as the greater distance of the roots from the air, their coming 

 into contact with the roots of other trees, or with a rocky or otherwise 

 unsuitable substratum, or the diminished elasticity of the bark ; and 

 though it is possible that trees might continue to grow in their fifth 

 century at the same rate as in their first, if the conditions remained 

 equally favorable, yet, since the proviso can never be insured, a fur- 

 ther difficulty, amounting to insuperability, occurs, to prevent such an 

 hypothesis from being brought to the test of either observation or ex- 

 periment. 



Whether, therefore, a tree might possibly continue living and 

 growing forever is a question of less entertainment than the question 

 of its possible duration in the common state of nature and under the 

 irreversible conditions of climate, soil, and the elements. What age 

 may we ascribe to some of our largest specimens, either still existing 

 or recorded in trustworthy history ? Is the period of one thousand 

 years, the favorite figure of tradition, a common or probable period 

 of arboreal longevity, or have our proudest forest giants attained their 

 present size in half the time that is commonly claimed for them ? 



In the discussion of this question we have but few known data to 

 guide us, since statistics of the rate of growth, as afforded by careful 

 measurement, date only from about the beginning of the eighteenth 

 century. Of such statistics we may dismiss at once measurement of 

 height or of the spread of a tree's boughs, the measurement of girth 

 being far easier and more conclusive. But it is unfortunate that no 

 standard of distance from the ground has yet been adopted for meas- 

 urement, so that the needless perplexity might be avoided which is 

 derived from giving the circumference now at the ground and now at 

 two, or three, or six feet above it. 



The counting of the rings added by exogenous trees every year to 

 their circumferences can only, without risk of great error, be applied 

 to trees cut down in their prime, and hence is useless for the older 

 trees which are hollow and decayed. Trees, moreover, often develop 

 themselves so unequally from their center that, as in the case of a 

 specimen in the museum at Kew, there may be about two hundred and 

 fifty rings on one side to fifty on the other. Perhaps the largest num- 

 ber of rings that has ever been counted was in the case of an oak felled 

 in 1812, where they amounted to seven hundred and ten ; but De Can- 

 dolle, who mentions this, adds that three hundred years were added to 

 this number as probably covering the remaining rings which it was no 



