72 FIELD, FOREST AND FARM 



if you count the ligneous layers removed before 

 reaching the metal sheet, you will find precisely ten, 

 just the number of years that have passed. 



"A number of observations like the following are 

 familiar : Some foresters cut down a beech bearing 

 on its trunk the date 1750. The same inscription 

 was found again in the inner substance of the wood, 

 but to reach it they had to cut through fifty-five lay- 

 ers on which no mark whatever appeared. If now, 

 we add 55 to 1750 we obtain precisely the year when 

 the tree was felled, or 1805. The inscription carved 

 on the trunk in the year 1750 had passed through 

 the bark and reached the layer of wood that was then 

 outermost. Since that event fifty-five years had 

 passed and new layers, exactly the same in number, 

 had grown over the first. 



' ' Thus a tree is composed of a succession of woody 

 sheaths, the outer ones enveloping the inner. The 

 stem or trunk contains them all; the branches, ac- 

 cording to their age, contain more or fewer. Each 

 one represents a single year's growth. The woody 

 sheath of the present year occupies the exterior of 

 the trunk, immediately under the bark; those of 

 former years occupy the interior, and the nearer 

 they are to the center the older they are. The lay- 

 ers of future years will come one at a time and take 

 their places over preceding layers, so that what is 

 now the outermost layer will in its turn be found 

 embedded in the body of the trunk. 



"Of all these ligneous zones of unequal age the 

 most important to-day is the outside one ; its destruc- 



