392 bulletin: museum of comparative zoology. 



face 26.18, at 45 fathoms, disregarding pressure, 26.30); and its 

 stability might be expected to increase as warming of the surface 

 progresses. Thus the process of winter cooHng on the surface, with 

 its consequent inversion of density, had come to an end by the begin- 

 ning of March at the mouth of Massachusetts Bay. 



It was a month before the Blue Wing resumed work; but in the 

 meantime Mr. Welsh had commenced his haddock investigation at 

 Gloucester, and on March 19, he occupied two hydrographic stations 

 at very nearly the same locality as our last station, nine miles south- 

 east from Cape Ann, in 45 and 65 fathoms of water. Mr. Welsh's 

 temperature records show a decided rise on the surface, which had 

 warmed to 39°, with the same temperature at 48 fathoms, the latter, 

 being unchanged from the last Blue Wing station. At 65 fathoms 

 the temperature was 38.8°, 1.5° colder than I found it at that depth, 

 and, indeed, generally over the bottom of the western half of the deep 

 basin, in summer. The salinity proved to be 33.17%o at the bottom, 

 at both stations, a decided rise from two weeks previous; and inter- 

 esting further because the deeper sample (65 fathoms) came from a 

 circumscribed basin, the shallower one from its rim, thus repeating 

 our experience in this same basin in July (Bull. M. C. Z., 1912, 58, 

 p. 65), when the bottom salinity was found to be the same as the 

 salinity on the bottom over the enclosing shoal. At the surface, over 

 the deep basin, the salinity was 32.84%c, precisely the same as it was 

 when the Blue Wing last visited this region: but over the rim it 

 was decidedly salter (33.01%^) : probably an evidence of vertical stir- 

 ring by tidal currents. 



On April 3, the Blue Wing occupied a station some five miles 

 southeast of Gloucester. By this time the surface temperature had 

 risen to 39.3°, being practically uniform down to 30 fathoms, and 

 slightly colder, 39.1° at the bottom, in 42 fathoms, the latter reading 

 showing a rise of only .1° from Mr. Welsh's records two weeks before. 

 And the fact that the temperature of the entire column of water had 

 risen slightly is good proof that tidal currents still caused active 

 vertical circulation, in spite of the increasing vertical stability of the 

 water, the conductivity of sea water being too slight for us to suppose 

 that the warmth of the surface had thus been propagated downward. 

 But though the temperature had followed the expected course, the 

 salinity had undergone a very striking change, for while the bottom 

 and intermediate Avaters continued to show the progressive increase in 

 saltness which had been taking place during the winter, with the very 

 high readings of 33.12%o on the bottom and 33.03%o at 25 fathoms, 



