378 
PACIFIC SCIENCE, VoL XIX, July 1965 
most westerly of the long north-south tracks. 
On these plots time is represented as a sequen- 
tial minute number beginning at 2110Z, Sep- 
tember 28. This particular plot follows 156° 10' 
W, and extends from 20°56'N to 23°20'N. 
The depth record begins on the shelf north of 
Maui, shows the drop into the deep, and rises 
onto the Arch, where it terminates. Negative 
excursions on the free-air anomaly curve, as 
are seen at time numbers 1580 and 1730, rep- 
resent erroneous readings caused by excessive 
acceleration corrections and are related to 
changes in ship speed. 
DISCUSSION OF COMBINED RESULTS 
In constructing the free-air anomaly contour 
map of the Moho Hole site area (Fig. 5), 
gravity results for the "Surveyor” north-south 
track were arbitrarily adopted as control data 
for correction of the other data. The first step 
was to correct the cross-cutting "Gilbert” lines 
of measurements. These in turn were used to 
correct the south-north "Surveyor” tracks. The 
adoption of the quartering sea north-south 
tracks as a control is in accord with results re- 
ported by Dehlinger (in press). The correc- 
tions adopted were -9, +7, and -23 mgal 
for the west, central, and eastern "Gilbert” 
long lines, respectively, and +15 mgal for 
each of the three south-north "Surveyor” lines. 
No adjustments were made for the lines close 
to the islands, as the Browne corrections were 
generally 100 mgal or less. 
It should be noted that the free-air anomaly 
I 
Fig. 4. Computer-plotted profiles of depth, observed gravity, free-air gravity anomaly, and magnetic force 
along a ship track of R/V "Surveyor.” 
