THE EARTH MOVEMENT ON THE FAULT OF APRIL 18, 1906. 145 
sidio, given in column 5 on page 143 which is the mean for the three complete 
years, May 1, 1904, to April 30, 1907, is adopted as being mean sea-level. The values 
given in column 4 of the table on page 143 are referred to the reading 8.514 feet (2.5951 
meters) as mean sea-level. Hence, a correction of — 0.138 foot (— 0.0420 meter) 
should be applied to these values to obtain the elevations now adopted as best. 
It is uncertain, as already indicated in this report, whether this correction of — 0.0420 
meter is due to improvement in the determination of the relation of mean sea-level to 
the tide-staff or to a subsidence of the tide-staff and adjacent bench-marks in 1904 or 
earlier, or to both. 
