SECT. 1] 



GRAVITY AT SEA 



155 



for instance, Figs. 16, 17, 18, 20, 23, 24 and 27). The following observations 

 were eliminated : 



1. Measurements in the shallow-water area inside the 2-km depth curve and 

 within 1J° (about 161 km) of the 2-km depth curve on continental and island 

 margins. 



2. Observations within trenches and within H° of the lip of the trenches 

 (the lip was considered to be the change from a steep to a gentle slope). 



3. Observations on ridges within the 4-km curves. 



About a quarter of the observations (numbering 1013) remained. These were 

 plotted on the Prince of Monaco charts. No simple pattern could be discerned 



Fip;. 13. Anomalies from pendulum measurements for "typical" ocean basins. (After 

 Wor/.el and Taiwan!, 19.^)9.) 



other than a latitude relationship. Fig. 13 shows the points plotted in relation 

 to the latitude. Fig. 14 shows the same data plotted as average values for 5° 

 intervals of latitude against latitude. The number of observations included in 

 each average is indicated in the middle graph, and the percentage of the Earth's 

 surface area between each 5° of latitude that is oceanic is plotted at the top. 

 For the oceanic part of the Earth it was concluded : 



1. From the average of all the values, the International Gravity Formula is 

 8.8 mgal too large. 



2. There is a definite asymmetry between the Northern and Southern Hemi- 

 spheres. 



3. The geoid is depressed below the ellipsoid from about 50°N to about 15°S 



