362 
Fig. 2. Bouguer anomaly map of Laysan I. 
PACIFIC SCIENCE, VoL XIX, July 1963 
174° I74®56‘ 
Fig. 3. Bouguer anomaly map of Lisianski I. 
southwest corner of the island, and values in- 
crease northeasterly to +278 mgal. Based on 
the observed gravity gradient, the center of the 
projected gravity high would lie to the north 
and slightly east of Nihoa and would have an 
estimated maximum Bouguer anomaly value of 
+ 310 mgal. 
Laysan 
The island is rectangular in shape, trending 
north-south. The Bouguer anomaly contours 
(Fig. 2) conform to the shape of the island, 
with the lowest value of +271 mgal located on 
the south end and the highest Bouguer anom- 
aly of +290 on the north end. The center of 
the gravity high appears to lie north and slightly 
east of the land mass. The gravity gradient on 
the island averages 10 mgal per mile. Assum- 
ing that the gradient remains constant, the cen- 
ter of the high will have a value of about 
+ 315 mgal. 
Lisianski 
This island is about one-half the width and 
length of Laysan and is elongated in a north- 
south direction. The Bouguer anomaly contours 
(Fig. 3) conform to the island’s outline. The 
