398 
PACIFIC EXPLORATION: J. F. HAYFORD 
observations are there. That will on examination prove to be a more 
weighty consideration in favor of the Pacific than appears at the first 
glance. 
Two other considerations also combine with this to indicate strongly 
that the Pacific is the most effective place to make gravity observations 
at sea in order to advance our knowledge of geodesy and geology. 
First, it is important to get observations at sea so far from any con- 
tinent as to be certainly free from any continental effect. 
It is difficult to get 2000 miles from all continents on the Atlantic. 
That distance is not sufficient. On the Pacific there is a considerable 
area 3000 miles from any continent. The Pacific ocean occupies the 
water hemisphere. 
The second consideration in favor of the Pacific is that it offers an 
unequaled variety of special opportunities to study special questions 
under extreme and contrasting conditions. In it there are small oceanic 
islands of volcanic origin far from land, and equally small oceanic 
islands far from land apparently not of volcanic origin. There are 
several troughs more than 8000 meters deep l3dng adjacent to large 
islands in some cases and in others far from any but very small islands. 
There are fiat bottomed areas of more than 6000 meters depth of various 
sizes, some covering several square degrees, and in various relations 
to land. There are several areas of less than 200 meters depth, some 
of which are far from any land, except very small islands. No other 
ocean offers an equal variety of equally favorable opportunities for 
special studies based on gravity observations at sea. 
Adequate observations of gravity, at sea, on the Pacific Ocean would 
contribute greatly to progress in geodesy and geology. 
1 Special Publication No. 10 of the Coast and Goedetic Survey, pp. 113-117 and Special 
Publication No. 12, pp. 18-21. Both these publications are under the title Effect of Topog- 
raphy and Isostatic Compensation upon the Intensity of Gravity. 
* "Neue Formeln fiir den Verlauf der Schwerkraft im Meeresniveau beim Festlande," 
von F. R. Helmert; Sitzungsberichte der Koniglich Preussischen Akademie der Wissen- 
schaften, 1915, XLI, Gesamtsitsung vom 21 Oktober. 
3 Special Publication No. 12 of the Coast and Geodetic Survey, pp. 24-26. 
