BIGELOW: EXPLORATIONS IN THE GULF OF MAINE. 51 



five as at Station 2. Below this level there was no further change of 

 temperature to 125 fathoms. 



At Stations 9, 11, and 14, (fig. 11) west of Jeffrey's Ledge, the 

 curves agree very well with those for Massachusetts Bay, except 

 that the surface temperature of the last two is several degrees lower, 

 and that at one Station (12b) in the trench, a lower bottom tempera- 

 ture, 39.2°, was recorded. But as this was the only instance of a 

 reading below 40.3°, it is possible that the thermometer recorded in- 

 correctly. Off Cape Cod at Station 43, late in August, the bottom 

 temperature was higher, in this case, 41.3° instead of 40.3°; and as at 

 Staton 2, the uniform bottom water was met at 50 fathoms (fig. 10). 



In all the western part of the Gulf, there was a bottom layer, of vary- 

 ing thickness, and reaching to within varying distances of the surface 

 of the water, the temperature of which was practically uniform, 40.3°. 

 In the western 100 fathom basin, it was seventy fathoms or more in 

 thickness, and it filled the deep circumscribed basin at the mouth of 

 Massachusetts Bay, as well as the bottom of the deep trough west of 

 Jeffrey's Ledge. But the differences in the temperature in Massa- 

 chusetts Bay in early July and late August (p. 58) show that it is only 

 below fifty fathoms or so that the bottom temperature may be expected 

 to remain fairly constant throughout the year. Above that level, the 

 whole water mass is subject to summer warming and winter cooling. 



If we compare the temperature sections at successive stations from 

 Cape Ann toward Nova Scotia (Stations 2, 7, 23, 24, 27, 28, 29, 

 figs. 8, 10) we find that the curves, which are nearly uniform from 

 the Cape to Station 24, grow progressively straighter from that point 

 eastward, the temperatures being higher and higher on the bottom, 

 lower and lower on the surface. And while the curves for Stations 

 27 and 28 show that the lower seventy to eighty fathoms of the 

 eastern arm of the 100 fathom basin, like that of the western one, 

 was filled with a layer of water which shows very little decrease in 

 temperature downward below thirty-five fathoms, the bottom water 

 differed from that of the western basin in being decidedly warmer 

 than in the latter, a difference which can not be laid to advance of the 

 season, because on our return (Station 41) we once more encountered 

 bottom water of 40.3°, west of Jeffrey's Ledge; and in being less 

 uniform, for it was slightly warmer at all depths at Station 28 than 

 at Station 27. And while at Station 28 the temperature of the whole 

 mass below thirty fathoms was 45.3°, at Station 27 there was a slow, 

 but constant decrease all the way to the bottom, where the tempera- 

 ture in 100 fathoms was about 43°. On reaching German Bank, we 



