1916] McEwen: Hfidrographic Ohseri'afioiis of Scripps Instilulion 265 



region at depths below about forty meters, as shown on page 277. 

 Therefore the presence of circumscribed areas of high salinity ad- 

 jacent to the island at the 55 and 92 meter levels (pis. 21 and 22, figs. 

 33 and 34), and the pronounced decrease in salinity as the distance 

 from the coast increases, afford additional evidence of upwelling. A 

 similar intrusion of water along the north and south borders, but 

 having a low instead of a high salinity, is indicated in these depths by 

 the dip in the bordering isohalines. 



Plate 22, figure 35, shows a circuruscribed area of water having a 

 high salinity which corresponds to the area of warm water shown by 

 plate 19, figure 28, and thus affords additional evidence in favor of a 

 whirl. 



C. RELATION OF TE.AIPERATURE AND SALINITY TO 

 DISTANCE FROM THE COAST 



From serial observations made at a selected number of positions 

 along any straight line, isotherms and isohalines can be drawn in a 

 vertical plane. From these isotherms and isohalines can be inferred 

 the flow of water in a direction parallel to the plane. 



1. Isotherms 



The isotherms in plate 23, figure 36, are based upon serial observa- 

 tions of temperature made along a line twelve miles in length running 

 perpendicularly to the contours from Point Dume. They show that 

 the inshore temperatures are, on the whole, lower than those offshore. 

 Furthermore, all of the lower isotherms bend upward as they ap- 

 proach the coast, thus revealing a flow of cold deep water toward the 

 coast along lines approximately parallel to the bottom. Again, their 

 greater upward deflection near the coast reveals a proportionately 

 greater upward veloeit.v of cold water there, although it is very small 

 at all positions. Since this upwelling of deep water would necessarily 

 result in a flow of cold water away from the coast in' the upper levels, 

 the figure ought to reveal, as it does, a rise in temperature in each of 

 the upper levels as the distance from the coast increases. This rise 

 in temperature would be expected to continue until the value corre- 

 sponding to the "normal" is reached, i.e., that value corresponding to 

 the local heating effect of the sun (see p. 258). 



