376 
PACIFIC SCIENCE, Vol. XIX, July 1965 
Fig. 2. Ship’s tracks of gravity and magnetic studies in the Hawaiian Islands area performed by vessels 
other than R/V "Charles H. Gilbert” and R/V "Surveyor.” 
of Molokai. Additional information was ob- 
tained from the preliminary BC 1604 and BC 
1605N charts of the U. S. Navy Oceanographic 
Office. Corrections were made for sound veloc- 
ity in Hawaiian waters using a temperature vs. 
depth curve derived from data in Seckel (1955), 
McGary (1955), Seckel (1962), and Murom- 
tsev (1963), and from the tables of sound 
speed in sea water (U. S. Naval Oceano- 
graphic Office, 1962). 
The speeds used on any one straight track 
were weighted means, weighted according to 
the time interval between successive position 
fixes. Ship’s position was determined from 
Loran C as well as radar and visual fixes. 
Gravity results were computed on the Uni- 
versity of Hawaii IBM 7040 computer, using 
an adapted program obtained from M. D. Hei- 
fer of the University of California at Los 
Angeles. 
NARRATION OF THE "SURVEYOR” OPERATION 
The "Surveyor” conducted underway grav- 
ity, magnetic, and bathymetric observation in 
the area north of Maui from 2110Z, Septem- 
ber 28, to 2026Z, October 2, 1964. Position 
plots for the ship’s track during this survey are 
shown on Figure 1. The tracks define a series 
of north-south lines spaced approximately 10 
miles apart. Six long lines centered on 155°45' 
W give good coverage of the area 120 miles 
north of Maui, over the Hawaiian Arch, where 
Shor and Pollard (1964) report depths to the 
mantle of about 9 km. West of this area four 
shorter lines cover an area 20 miles north of 
Molokai and Maui, where Shor and Pollard 
(1964) report sub-Moho seismic velocities at 
depths of 5.8-7 km. This area is also charac- 
terized by a large positive magnetic anomaly 
( Malahoff and Woollard, in a forthcoming issue 
