- BIGELOW: OCEANOGRAPHY OF MASSACHUSETTS BAY. 393 
(fig. 2) the surface salinity had fallen from 32.8%, to 32.3%p (fig. 3), 
which is, of course, good evidence that the influx of river water was 
beginning to flood the surface. And from the standpoint of dynamics 
this phenomenon is important, because it suddenly lowers the surface 
density to a marked degree, with consequent increase in vertical 
stability. Unfortunately only two more stations were occupied in 
Massachusetts Bay during the spring; but though both were so close 
to land that they are not strictly comparable with the data acquired 
further offshore, they show the advance of the general vernal hydro- 
graphic change. Thus on April 14, two miles off the mouth of Glou- 
cester Harbor, the surface temperature had risen to 42°, the 25 
fathom reading (bottom) being about the same as at the last station 
(39.4°). And on May 17, the surface water off Magnolia had warmed 
up to 47.3°, with 45.1° at 9 fathoms. Salinity meantime had fallen 
to 31.11%, on the surface, 32.79%, at-25 fathoms, on April 14: and it 
continued to fall, reaching 30.95%, on the surface, 31.25%, at 10 
fathoms on May 17. 
TEMPERATURE AND SALINITY NORTH OF CAPE ANN, 
Marcu AND APRIL. 
Mr. Welsh’s oceanographic data for these months were taken chiefly 
in three general regions, 2. ¢., the neighborhood of the Isles of Shoals, 
near Boon Island, and a few miles off the coast between Cape Porpoise 
and Wood Island (Plate); and though his stations were chosen pri- 
marily for their fisheries interest, they proved to be well located for 
| oceanographic purposes. The first two grounds together cover an 
area of some fifteen miles from northeast to southwest; but there 
is no important separation between the two, so far as temperatures 
are concerned. ‘The salinity of the area, however, is less uniform, be- 
cause subject to the immediate influence of the Piscataqua River. 
The Cape Porpoise ground, though nearer in actual distance to the 
Boon Island stations than the latter are to the Isles of Shoals, was very 
distinct hydrographically. 
; The Boon Island ground was visited on March 29, April 4, April 5, 
' and May 14, while from April 22 to May 16 frequent observations 
were taken close to the Isles of Shoals and between them and the 
coast. On the first date the water was coldest at the surface, the 
readings being 38.3° at the surface, 38.7° at 17 fathoms, and 38.9° 
_ at 35 fathoms; 7. ¢., winter conditions still prevailed (fig. 4), although 
