THE OAK. 



21 



sides, tapering more gradually, assume a perpen- 

 dicular direction, and for some height form a 

 cylinder. After that a greater circumference be- 

 comes necessary for the insertion and establish- 

 ment of the principal boughs^ which produce a 

 swelling of its diameter. Hence may be deduced 

 an idea of what the proper shape of a column of 

 the greatest stability ought to be to resist the 

 action of external violence, when the quantity of 

 matter is given whereof it is to be composed. 

 Upon this model, therefore, on the 25th of 

 August, 1759, Mr. Smeaton completed his light- 

 house, being the third structure of the kind which 

 had been raised on the dangerous rock from which 

 it derives its name." How "wisely he acted in 

 choosing Nature for his instructress, may be 

 inferred from the fact that it has now stood 

 eighty-six years without requiring any essential 

 repairs. 



The trunk of the Oak, thus perfectly adapted 

 as it is by its form to resist the most violent action 

 of the wind, derives additional strength from the 

 slow rate of growth of its timber. A very small 

 quantity of woody fibre is deposited every year, 

 but it is proportionately dense and solid, and the 

 concentric annual layers are very firmly united. 

 Hence it is admirably prepared to withstand 

 lateral -vdolence, as well as to support its enor- 

 mous superincumbent weight of branches ; while 

 its tap-root, descending perpendicularly to a 

 great depth, and its tortuous underground arms 

 proceeding horizontally at a greater depth be- 

 neath the surface than those of most other 

 trees, are equally efiicacious in resisting any 

 upheaving force to which its spreading and 



