CHRONOLOGY OF TREES. 149 



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(1849,) two hundred and ninety layers of growth. Mr. S. 

 O. Knapp saw another tree with three hundred and ninety, 

 and another gentleman one of four hundred rings or layers 

 standing in one of the ancient pits. On the mounds and 

 earthworks of Ohio, the timber is as large as it is in the 

 surrounding forest. 



Mr. Tomlinson, the owner of the Grave Creek Mound, 

 twelve miles below Wheeling, on the Virginia side of the 

 Ohio, cut down an old oak which stood upon it, having 

 been, in 1838, about hlteen years dead. It had about fiye 

 hundred layers of growth. This place was visited as early 

 as 1734, and the trees were then old. If, therefore, we can 

 rely upon this mode of reckoning time, in cases where 

 history and all other records are silent, something will be 

 gained to chronology. 



The instances I have here prepared, show that the rule 

 is not absolute, but that circumstances modify the regu- 

 larity of the accretion of wood or annular coatings, and 

 that, as a general rule, only one is formed in a season. 

 There are cases of very thrifty young shoots that make 

 more than one course in a year, but they are rare excep- 

 tions to the above rule. Trees that are transplanted, 

 frequently lose a season's growth, and this is shown by the 

 table, for the reputed ages of the trees which are noticed 

 there is greater than the number of the rings. A severe 

 drought may produce the same result. It is not easy 

 always to count them exactly, because the divisions are 

 frequently obscure, and it makes a difference as to the 

 height above the ground the stump is cut. A small sugar 

 tree, which I cut near the ground, had from ten to twelve 

 rings of growth where it was 1.70 inches diameter, and 

 again, at five feet from the ground, with a diameter of 1.40 

 inches, it had but seven. 



There may be, in this mode of determining the age of 

 trees, a liability to error from these causes of a few years 

 but the error is likely to be one of diminution. 



