276 OUR NATIONAL PARKS 



organs. Only the leaves die of old age, their 

 fall is foretold in their structure ; but the leaves 

 are renewed every year and so also are the other 

 essential organs — wood, roots, bark, buds. 

 Most of the Sierra trees die of disease. Thus 

 the magnificent silver firs are devoured by fungi, 

 and comparatively few of them live to see their 

 three hundredth birth year. But nothing hurts 

 the Big Tree. I never saw one that was sick or 

 showed the slightest sign of decay. It lives on 

 through indefinite thousands of years until 

 burned, blown down, undermined, or shattered 

 by some tremendous lightning stroke. No ordi- 

 nary bolt ever seriously hurts Sequoia. In all my 

 walks I have seen only one that was thus killed out- 

 right. Lightning, though rare in the California 

 lowlands, is common on the Sierra. Almost every 

 day in June and July small thunderstorms re- 

 fresh the main forest belt. Clouds like snowy 

 mountains of marvelous beauty grow rapidly in 

 the calm sky about midday and cast cooling 

 shadows and showers that seldom last more than 

 an hour. Nevertheless these brief, kind storms 

 wound or kill a good many trees. I have seen 

 silver firs two hundred feet high split into long 

 peeled rails and slivers down to the roots, leav- 

 ing not even a stump, the rails radiating like 

 the spokes of a wheel from a hole in the ground 

 where the tree stood. But the Sequoia, instead 

 of being split and slivered, usually has forty or 



