264 Vnivcrsify of Califoniia Publications in ZooIogiJ [Vol. 15 



23), reveal the same type of cireulatiou in which however, the relative 

 influence of the southerly drift decreases as the depth increases. 



At the depth of eighteen meters an area of cold water is shown 

 surrounded by warmer water and by the coast (pi. 16, fig. 22). A 

 similar distribution of temperature is revealed at each of the five lower 

 levels examined, namely 27, 37, 55, 64, and 92 meters (pis. 16-18, figs. 

 23-27). Such a distribution of temperature reveals either an upwell- 

 ing of bottom water adjacent to the coast combined with a flow away 

 from the coast, or an upwelling extending over nearly the whole area 

 lying between two lines running southwest from the land. It has. 

 been shown that the former type of circulation characterizes the upper 

 layers of water; therefore there must be a compensating circulation 

 of the latter type in the deep water. Moreover, Ekman's theory 

 (see p. 277) shows that the former type of circulation is usually con- 

 fined to the upper fifty meters, and the latter type prevails from there 

 to the bottom. 



On the whole, there is a decrease in temperature at each level along 

 lines converging to the western coasts of the islands. The decrease, 

 however, is not so pronounced as would be expected under similar 

 conditions off the mainland, because their short coast lines permit the 

 intrusion of water at all levels. 



The circumscribed areas of warm water shown off South Island by 

 plate ] 5, figure 20, may be whirls formed by the junction of a south- 

 ward drift of warm water between the islands and the westward drift 

 of upwelling cold water. Similar areas of warm surface water are 

 shown by plate 19, ba.sed upon observations made during ilay, 1914, 

 and July. 1912. 



(h) Isohalincs. — The isohalines in plate 20 show the junction of 

 a southward flow of the upper layers of water having a high salinity 

 with a westward flow of water of low salinity derived from the up- 

 welling next to the coast of South Island. A tendency of the two 

 currents to form whirls is indicated by the circumscribed areas of high 

 salinity in both dejiths. 



The areas of salinities as low as 33.50''/(,o at the depth of 27 meters 

 (pi. 21, fig. 32) , bounded by the coast and by water of a higher salinity, 

 show upwelling; while the southward dip of the 33.60Voo line at the 

 north and the northward dip of the 33.66V(|„ line at the south indicate 

 an intrusion, along the borders of this area, of water having a higher 

 salinity. 



High salinities should border the western coasts in this upwelling 



