28 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
curves, it can be shown that these distances are a little less than four-tenths the observed 
distances between C”D’ and C’Q”, at equal distances from the fault. The observed 
southerly displacement of Mount Tamalpais between 1874-1892 and 1906-1907 was 0.58 
meter; its northerly displacement between 1874-1892 and the beginning of 1906 must 
have been about 0.22 meter; and therefore its actual southerly movement at the time 
of the earthquake must have been 0.8 meter; and the opposite displacements of Mount 
Tamalpais in the two intervals would have occurred independently of the shifting of the 
underground flows. | 
If instead of considering the displacements roughly symmetrical and in opposite direc- 
tions on opposite sides of the fault-line, we prefer to consider that they were all northerly, 
the conditions are represented in figs. 15 and 16; they are satisfied by the supposition of a 
single, northerly flow extending for some distance to the west, increasing to a maximum at 
D and diminishing rapidly to zero in the neighborhood of O (broken line in fig. 16). The 
southern force between O and C would be referred to the resistance which the underlying 
material would offer to the displacement of the crust above it.’ 

1 Mr. Bailey Willis, on account of the forms of the mountain ranges bordering the Pacific Ocean, 
has concluded that the bed of the ocean is spreading and crowding against the land. He thinks in par- 
ticular that there is a general sub-surface flow towards the north which would produce strains and earth- 
quakes along the western coast of North America. Science, 1908, vol. xxvu, p. 695. 
