658 PROTECTION AGAINST LIGHTNING. 



Fire Insurance Company agreed to insure against damage by 

 forest fires throughout Germany, and appointed a forest 

 expert as manager of this branch of their business. 



The company insures standing crops of trees up to the age 

 of 60 years, and felled timber as long as it is the property of 

 the insurer. Damage in burned forests is assured at its cost- 

 value whenever this exceeds its actual value. The premia 

 vary according to the greater or less danger of particular 

 crops from 45 pfennigs to 4 marks per 1,000 marks of their 

 insured value. For ordinary crops 1 60 years old 



Pure broadleaved woods . . - 85 marks. 



Mixed coniferous ,, . .1*20 



Pure coniferous ,, . . 2'00 

 In Switzerland, insurance against fire has been effected 

 (1906) at 10 per cent, of the endangered capital. 



In Belgium, insurance can be effected against forest fires at 

 the following rates of premium per 1,000 francs value : 



Broadleaved woods . . 60 centimes. 



Conifers under 20 years old . 6 francs, 

 over . 5 francs. 



SECTION II. EFFECTS OF LIGHTNING ON TREES.* 



Much has recently been written about lightning and its 

 effects on trees, but the causes of thunder-storms are not yet 

 clearly known. The action of lightning on trees also requires 

 further study. 



1. Mode of Striking. 



When lightning strikes a terrestrial object it is termed a 

 "direct stroke" 



It is termed hot when it sets fire to the object, it is otherwise 

 cold. 



A lack-stroke occurs when the accumulated positive or 

 negative electricity at the top of an object, such as a tree, 



* Klein, " Das Gcwitter und die dasselbe begleitenden Erscheinungen." Graz, 

 1871. 



Baur, " Der Blitz als Waldverderber," " Monatschrift fur das Forst. u. 

 Jagdwesen," 1873, p. 97. 



Rippold. " Die Enstehung der Gewitter." Frankfurt-a.-M., 1897. 



