386 bulletin: museum of comparative zoology. 



The subsurface temperatures were all taken with the Negretti and 

 Zambra reversing thermometers; the water samples with the stop- 

 cock water bottle previously described (Bull. M. C. Z., 1914, 58, p. 37, 

 fig. 1). The purpose of our plankton work being chiefly qualitative, 

 we depended on horizontal tows, at different depths, with the 4 ft. 

 net used on the Grampus (Loc. cit., p. 39) beside various small nets. 

 The salinities listed below were all obtained by titration. Each sample 

 was tested twice, by Mr. Welsh, or myself, standard water being sup- 

 plied by the International Committee for the exploration of the sea. 



Temperature and salinity, south of Cape Ann. 



When we ceased work on the Grampus at the end of August, 1912, 

 the surface temperature was about 60° over the northern half of 

 Massachusetts Bay, a noticeable cooling having already taken place 

 from the summer maximum of 64° to 66°; and though there was a very 

 rapid temperature decline from the surface downward to about 44.5° 

 at 30 fathoms and 43° at 40 fathoms, the bottom temperatures in 

 general at 30-40 fathoms were several degrees warmer than they had 

 been at the beginning of July ; the exact readings varying from place 

 to place, consequent on tidal currents {Loc. cit., p. 48). The salinity 

 at the end of August was about 31 .6 on the surface, 32. 55%^ at 30 fath- 

 oms over the northern half of the Bay; 31.9%^ at the surface, 32.6%o 

 at 30 fathoms, 32.9%c at 40 fathoms over its central portion, showing 

 practically no change from the early part of July; and the water of 

 the Bay was in stable equilibrium, the density (at the temperature 

 in situ) being about 23.2 at the surface, about 25.5 at 30 fathoms. 



On resuming work on November 20 (fig. 1, 3) it was found that the 

 surface temperature had dropped to 48.5°, but the reverse change had 

 taken place on the bottom, for while the 30 fathom temperature was 

 44.7° on August 31, on November 20, at nearly the same locality, 

 it was 48° both at that level and at 25 fathoms. Thus the mean 

 temperature for the whole column of water had fallen less than one 

 degree, being about 49° on August 31, and 48.2° on November 20. 

 The salinity (fig. 2), like the temperature, was nearly uniform with 

 depth on November 20, being 32.57%^ at the surface, 32.57%o at 25 

 fathoms; 32.6%o at 30 fathoms, a degree of saltness about the same as 

 the bottom salinity in this region at the end of August, and con- 

 siderably higher than the mean salinity of the entire column of water 

 at that time (August 31, Station 10,046, mean salinity 32.2%c). Den- 



