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bulletin: museum ob' comparative zoology. 



raised as surface temperature is lowered by the upwelling of cold 

 saline waters consequent on the several northwest gales already men- 

 tioned, or by the mixing of the upper few fathoms by Avave action. 

 An excellent example of the effect of the latter is afforded by two 

 successive stations, April 26 and 29, a few miles outside the Isles 

 of Shoals. On the former day the surface salinity was 30.03%o, 

 when a northeast gale and heavy sea mixed the water sufficiently to 

 raise the surface to 31.5%o, and to lower the 15 fathom salinity from 

 32.45%c to 32.3%c, the bottom salinity remaining the same (fig. 5), 

 the fact that the average salinity of the entire column of water had 



Fig. 5. — Salinity sections near Boon Island March 29 (Station 5 W. W. 

 Welsh) : April 5 (Station 8 W. W. Welsh) ; and April 25 (Station 18 W. W. 

 Welsh) ; and east of the Isles of Shoals, April 26 (Station 19 W. W. Welsh) 

 and April 29 (Station 20 W. W. Welsh). 



risen only from 32%o on the 26th to 32.15%o on the 29th showing 

 that there had been very little influx of salt water from off shore. 



The effect of a northwest wind, with consequent upwelling of bot- 

 tom water, is illustrated by the sections for April 16 and 22 (Stations 

 13 and 16 Welsh, fig. 6), which show how the salinity of the entire 

 column of water was raised by this process (mean salinity, Station 13 

 Welsh, 31.7%o: Station 16 Welsh, 32.0%o), though most markedly 

 near the surface. And the fact that the rise is evident at the bottom 

 (25 fathoms) shows that the influence of the wind causes an inshore 

 movement of bottom water from greater depths further to the east, 

 while the next salinity section (Station 17 Welsh, fig. 6) shows that 

 this movement continued at least a day after the surface freshening 



