LOCAL EFFECTS OF SAN FRANCISCO EARTHQUAKE 311 



intensity of the shock at different places, the best evidence was 

 supphed by the oak trees broken and uprooted where the intensity 

 was greatest, by the percentage of country water-tanks thrown down, 

 and, as the intensity decreased, by the condition of plastering in 

 houses and the number of brick chimneys found standing. 



There are many white oaks (Quercus lohata) growing in the 

 valleys through this section of the country, and in a belt extending 



Fig. 8. — An oak tree six feet in diameter uprooted by the earthquake three hun- 

 dred yards from the fault line. 



for not more than 400 or 500 yards on each side of the fracture many 

 of these trees have been uprooted or have had large branches whipped 

 off. Sound limbs 2 feet thick were broken off by the shock, and 

 there are trees having a diameter of more than 6 feet that were over- 

 turned during the earthquake. About 300 yards southwest of 

 Searsville Lake a live oak {Quercus agrifolia), growing within a 

 few feet of the fracture, was split down the trunk by the violence 

 of the movement, but is still standing. 



On Cahill Ridge, 2 miles southwest of the fault-line, there are 



