STORMS. f)33 



The rates of storms are yiven as follows by House : — 



Yards iMiles 



per second. j)er hour. 



Storm, or tempest ... 24 50 



Great storm .... 29 60 



Hurricane ..... 40 80 



Destructive hurricane . . 41) 100 



2. Damacfc done. 

 A. General Account. 



Storms shake the roots of trees up and down in the ground 

 and may either give a tree a decided leaning in a particular 

 direction, or tear it out of the ground by its roots and with 

 the earth adhering to them, or break its stem or branches. 

 Such uprooted or broken trees are termed icindfaUs. 



Whether the tree is blown down or broken depends 

 partly on the intensity of the storm and partly on the 

 relative power of resistance of its roots or stem. Breakage 

 happens when the roots resist better than the stem, windfall 

 when the roots are the weaker. Breakage may also be due 

 to one tree falling on others. The amount of resistance 

 to storms which the roots or stem of a tree offers, equal con- 

 ditions being presupposed, depends on the nature of the soil 

 (its compacity and degree of moisture, e.g., whether its resist- 

 ance has been weakened by heavy rain before a storm), and 

 that of the loealiti/ (plains, or hillsides, aspect, gradient, etc.). 



Independently of the above, the storm -firmness of our trees 

 varies according to species, lenf/th of bole, nature of crown, 

 sotoidness of the wood, densittf of crop, mode of formation, and 

 tendimi, as well as on other local circumstances. Each of 

 these factors will be considered separately. 



The roots of the trees that are stretched by the wind are 

 termed anchor-roots, those on the lee side of the tree projy-^ 

 roots. The prevailing opinion is that the anchor-roots hold 

 up the tree against a storm, as the anchor holds a ship. 

 Hesse, however, agrees with Nordlinger in attaching more 

 importance to the prop-roots. In support of this he states 

 that in a roadside avenue running N. and S., the trees on the 

 \\ ., having their prop-roots in the firm road, hold better against 



