BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 51 
mouth of Vineyard Sound, on the same day, the surface temperature was 67° F. Tem- 
peratures were likewise taken west of No Mans Land and south of Narragansett Bay 
in 29 fathoms. These agree in being considerably lower than the temperatures known 
to occur at the same time in the more inclosed waters of the neighborhood. The pres- 
ent writers have found still more extreme conditions to prevail at certain points imme- 
diately to the east of Cape Cod. At Crab Ledge, a few miles to the east of Chatham 
(chart 223), at a mean depth of 17% fathoms, two observations on August 12, 1909, 
gave a mean surface temperature of 65° F. and a mean bottom temperature of 47.2° F. 
These figures accord pretty well with some obtained at nearly the same point by Robert 
Platt, United States Navy, on September 14 and 15, 1877.4 ‘The latter found a mean 
surface temperature of 60.3° F. and a mean bottom temperature (28 fathoms) of 48.2° F. 
It is interesting to compare the figures obtained by us on August 10 and 12, 1909, for 
a series of points between Woods Hole and Crab Ledge. These are presented in the 
following table: 
Surface | Bottom 
Depth temper- | temper- 
ature. ature. 
inci keien(aist without Nantucket Sound) aise cree a Se rlacelehi jays cies 5.aieleiesajo ere ele jsie spsiepe einer sick Fe 63-0 62.0 
Handkerchief Shoal (eastern end Nantucket Sound)... .........0 22. eee eee eee ee eee eeeee 7 62.5 60.0 
rossi Cniddile of Nantticket Sound) 2: P2502 5.fcce ac cos We Feeie aisle cals viele clsebsieewielelele oat hee 834| 270.5 @ 70.2 
West@hop (easter end wv ME VAard! SOUNG) &o%\-j).2> ciclelei as c.a siekls ojaieicaa «'s eiors old.cisieisinibisjars @aislorsismtaleinis ac 12 71.0 69. 5 
@ The mean of two determinations on,different days. 
Verrill explained the low temperatures of the outer waters by invoking the aid 
of ‘‘an offshoot of the arctic current,’ which he believed to pass westward into Long 
Island Sound. The question whether or not there is a definite southward (and west- 
ward) flowing current which affects this part of the coast has already been discussed 
briefly on another page. No conclusive answer to this question appears to be forth- 
coming at present. Undoubted, however, is the fact that during the summer months 
there lies a comparatively cold zone between the warm coastal water and the yet warmer 
Gulf Stream. This may, as has been suggested, merely represent the normal ocean 
water which would be proper to this latitude in the absence of the Gulf Stream. If this 
view be accepted, the higher temperature attained during the summer months by the 
waters of Buzzards Bay and of Nantucket and Vineyard Sounds is simply the result 
of their shallowness and comparative detachment from the great reservoir of ocean 
water outside, just as we know that salt marshes or shallow lagoons become even 
warmer than this during the summer months. 
The question here suggests itself why the coastal waters north of Cape Cod, e. g., 
at Gloucester and at Boothbay, do not likewise become much warmer than they do 
during the summer months. We have seen (p. 49) that the relations between the 
temperatures at these points and those at Woods Hole are not such as are wholly 
explained by differences in latitude. It is highly probable that one factor in the case is 
the far greater depth of the waters north of Cape Cod, at slight distances from shore, 
For example, the 50-fathom line passes within from 5 to 10 (nautical) miles of Cape 
Ann and of many parts of the Maine coast; while at the nearest point it lies over 50 
a These data were furnished us by the Superintendent of the Coast and Geodetic Survey. 
