SECT. 5] 



SEASONAL CHANGES IN SEA-LEVEL 



489 



Indian Ocean except the Gulf of Siam, in the western third of the Pacific both 

 north and south of the equator, and around the southern half of Australia. 

 Small positive deviations (between and + 5 cm) occur at gauges in the central 

 South Pacific, along part of the eastern seaboard of the United States, and at 

 several locations in the tropical and subtropical Atlantic as indicated by the 

 zero contour there. The deviations of largest magnitude are: —18 cm in the 

 Gulf of Siam, — ] 3 cm along northern Norway, + 30 cm in the Bay of Bengal 

 and +14 cm along southern Australia. 



To a first approximation, the December chart (Fig. 4) shows positive devia- 

 tions where negative ones appear in June, and vice versa, but one would hardly 

 like to call these charts mirror images of each other. Largest positive values in 

 December are + 20 cm in the Gulf of Siam and +16 cm along Norway ; negative 

 deviations reach — 26 cm in the northern part of the Bay of Bengal and — 10 cm 



Fig. 4. November, December and January deviations. (See Fig. 1.) 



in southern Australia. Noticeable discrepancies from any mirror-image relation- 

 ship occur around India, on the Pacific coast of Central America, and, perhaps, 

 in parts of the Central South Pacific. All three of these areas have positive 

 deviations both in December and in June ; the deviations are small, and 

 therefore somewhat indeterminate, except around India. 



During the I.G.Y. the Arctic Ocean was ringed for the first time with tide 

 gauges, although the distribution was sparse and, of course, no gauges could be 

 installed except attached to the land-masses around the edge of this body of 

 water. Gauges located north of the Arctic Circle include ten in the northern 

 part of Norway, plus the following : 



