26 



Sierra Club Bulletin. 



driving the tip of its axis into the ground to a depth of about 

 four feet, as near as could be determined. 



The crown then toppled over northerly, leaving an imperfect 

 shell of wood and bark around the circumference of the ground 

 hole. The lower portion of the crown's axis does not lie along 

 the ground, since it fell across and is consequently raised off 

 the ground by a log fragment from the middle portion of the 

 trunk, which had fallen previously, as just described. All 

 around the tree in every direction to a total distance of one hun- 

 dred and forty-four feet the ground was littered with wood 

 and bark fragments six inches to a foot long or more, all the 

 fragments much alike in that they were fractured sharply and 

 not splintered. A great fragment of the trunk, twenty feet 

 long and two feet wide, was thrown thirty feet from the base. 



Benjamin Franklin apparently was the first to suggest that 

 the explosive action of lightning upon trees was caused by the 

 effect of the intense and sudden heat in vaporizing the water 

 content of the trunks. 



In the case of the Kern Cafion tree the lightning stroke did 

 not start a fire. It may be possible that fire does not commonly 

 occur in connection with highly explosive strokes, an idea which 

 is only offered by way of suggestion. If, however, such were 

 the case, it would follow that fire is likely to occur only where 

 the current is fed off slowly enough to cause ignition of leaves, 

 dry bark or punky wood. The explanations of the effects of 

 lightning on trees are little understood,* but the explosive 



* The present state of knowledge is well summarized in "Lightning in Relation 

 to Forest Fires" (U. S. Forest Service, Bulletin iii), a highly valuable and inter- 

 esting research by F. G. Plummer. The author of this bulletin speaks of explosive 

 action as resulting from upward stroke. 



"It has been held, though not proven," says Mr. Plummer, "that the Big 

 Trees of California are repeatedly struck by lightning, and that although not killed, 

 their leaders are broken and their tops stunted in consequence." In the "Silva of 

 California" I made the statement that the tops of Big Trees may be killed by 

 lightning. This statement was made upon the basis of reports by careful observers 

 who have lived for periods of ten to twenty years in or near the Sequoia National 

 Park. Careful and explicit details have been made to me concerning individual 

 Big Trees on fire in the top in cases where the fire did not originate from ground 

 fires or forest fires. Such instances attract particular attention, partly because a 

 Big Tree with the tip of its axis on fire 200 feet above the ground presents a unique 

 spectacle, more especially at night, and partly because such fires often give rise to 

 ground fires in the forest by throwing off live sparks. 



The Kern Canon tree described above stood in a lonely and remote part of the 

 Sierra Nevada. It is therefore interesting to learn that the destruction of this 

 particular tree was witnessed by a Porterville man in June, 191 2, and that his 

 account of what happened essentially verifies the relation given in this paper. 



