1916] McEwcn: Hiidrof/rapliic Obs( rrafions of Scripps Instil ul'mn 263 



evaporation to cool the water. Hence such a complex distribution of 

 temperature and salinity must often arise as to require other data 

 before trustworthy conclusions relative to oceanic circulation can be 

 reached. Again, we must not forget that the complexities indicated 

 are due in part at least to eri-ors of interpolation (see p. 259). Foi' 

 example, the oval area of warm water off the mainland near La Jolla, 

 shown by plate 5, indicates the presence of a whirl, but (pi. 13) the 

 salinities in the central part of the oval are low, although high ones 

 would be expected if this water were comparatively stagnant. Again, 

 the isotherms in plate 14, figure 18. indicate at the same location a 

 similar whirl which is apparoitiy cdntradicted by the eorresiionding 

 isohalines (pi. 14. fig. 19). 



On the whole, the isotherms and isohalines show an increase in 

 temperature and salinity with a decrease in latitude, and afford strong 

 evidence of a general southerly drift that at times is combined with 

 a northerly current near the mainland. This southerly flow largely 

 consists of water having low temperatures and salinities that are very 

 probably due to upwelling of bottom water adjacent to the mainland. 

 There is also evidence, although not as strong, of the presence of areas 

 of whirling water whose central parts are comparatively stagnant. 



2. Surface .vnd Subsurf.vce Isotherms and Isohalines West of the 

 CoBONADO Islands 



The large number of observations made in the region of Los 

 Coronados (the Coronado Islands) justifies dividing that area into 

 sections whose sides are one minute in length and representing in 

 greater detail the distribution of temperature and salinity. The 

 isotherms and isohalines which will be considered first are based on 

 observations made in each of a series of depths during June, 1911. 

 The shaded area of each figure represents a horizontal section of the 

 land at the depth considered, i.e., the boundary of this area would be 

 the shoreline if the water were lowered to the corresponding level. 



(ff) Isotherms. — The dip to the southwest of the surface isotherms 

 in the upper part of plate 15, figure 20, and the presence of colder 

 water along an area extending to the southwest from the islands are 

 probably due to the junction of a southwesterly current of warm 

 water, pointed out on page 259. with a westerly current of cold water. 

 The i.sotherms at the depths 9. 18. and 27 meters (pis. 15-16. figs. 21- 



