120 



MISCELLANEOUS. 



PT. II. 



each year, — in less than a century, that is in ninety-six 

 years, it will be even with the surface, and in another 

 century it will be one foot above the siuface. Without 

 contravening circumstances, this rising of the roots 

 may be seen around all old trees. 



In the growth in girthing of tlie roots, the earth 

 above the roots is easily displaced, that on tlie sides 

 with more difficulty, and the earth below roots 

 with still greater difficulty. In proportion, then, as 

 the surface against which the lower sides of roots 

 grow is unyielding, each root has a tendency to upheave 

 itself bodily, besides the rising at its upper surface from 

 what is called the growth by juxta-position ; and the 

 whole mass of roots have a tendency to upheave the 

 whole tree. In the case of roots growing on rock this 

 upheaval must take place, or the roots must cease to 

 grow on their lower sides. 



In the observation above in regard to the lateral 

 upward growth of roots, credit is only taken for half 

 of the growth in diameter, that is for l-8th of an inch 

 growth, on the upper side of the root. The other 

 l-8th of an inch growth on the lower side is supposed 

 to displace the earth downward. I think it, however, 

 likely, in the generality of cases, tliat, owing to the 

 resistance of the subsoil, the progress of the root up- 

 ward is equal to nearly the whole of the growth in 

 diameter ; and that, in proportion as the deposit of new 

 growth below the root decreases from mechanical pres- 

 sure, the new deposit above the root increases. I have 



