1899.] PUBLIC DOCUMENT — No. 33. 167 



the alternating current the anode and cathode alternate very 

 quickly, while in the direct current no alternation takes 

 place, and this results in an electrolysis of the cells, which 

 in turn produces disintegration and quick death to the pro- 

 toplasm. In short, we may say that all of the injury to trees 

 by electricity is brought about by heating, and by electroly- 

 sis and disintegration of the cell contents. Some observa- 

 tions made by Professor Ilartig of Munich upon the effects 

 of lightning on trees are interesting in connection with the 

 subject of electricity. He observed that when a tree is 

 struck by lightning the current usually travels along the 

 cambium /one or living layer of the tree, just under the 

 bark, inasmuch as at this point the current finds the least 

 resistance. Sometimes the burning effect is more marked 

 just inside and outside of the cambium layer, where the re- 

 sistance is slightly greater, — a feature which is shown by 

 the dead areas in the trees many years after. There are 

 many trees struck by lightning which show scarcely any 

 injury, and others will show only a small dead area which 

 coincides with the path of the current. Professor Hartig 

 has made many observations upon trees struck by lightning, 

 and his practised eye is able to detect trees that have been 

 so affected which to the ordinary observer would appear 

 perfectly sound. 



