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PACIFIC SCIENCE, VoL XIX, July 1965 
and the readings varied by less than 0.15 mgal 
during the six days of the field work. Correc- 
tions for instrumental drift and tidal effect, 
therefore, were neglected in the calculations, as 
their combined effects amount to only a few 
tenths of a mgal. The data were corrected for 
elevation above sea level and effects of above- 
sea-level terrain within about 100 miles of 
each station. An assumed average rock density 
of 2.3 g/cc was used in the Bouguer and topo- 
graphic corrections. Topographic corrections 
were made at about 15% of the stations; cor- 
rections at other stations were estimated on the 
basis of the calculated corrections. 
Observed gravity values are believed to be 
accurate to at least 0.5 mgal. The elevations of 
bench marks and spot elevations are known 
within ±5 ft of their true elevations, and the 
altimeter-determined elevations are believed to 
be accurate within ±25 ft. In terms of a com- 
bined free-air Bouguer correction, these eleva- 
tion uncertainties would correspond to errors 
of 0.3 mgal and 1.6 mgal, respectively. Topo- 
graphic corrections are probably correct to 
within 10%. Hence, the largest topographic 
corrections, such as the 40- to 50-mgal values 
obtained at the summits of West Maui and 
Haleakala volcano, can introduce errors up to 
5 mgal. However, most of the stations had 
topographic corrections of less than 20 mgal, 
so probably the complete Bouguer anomaly 
value, at most stations, is accurate to at least 
3 mgal. 
REFERENCE 
Hawaii Institute of Geophysics. 1965. 
Data from gravity surveys over the Hawaiian 
Archipelago and other Pacific islands. Hawaii 
Inst. Geoph. Rept. 65-4, March 1965. 10 
tables. 
