BIGELOW: EXPLORATIONS IN THE GULF OF MAINE. 85 



the current charts which have appeared show a southwest flow along 

 the outer edge of George's Bank, next the Gulf Stream, it is a question 

 whether this flow is a contant, or even a dominant one. 



Surface and bottom currents. — To obtain a satisfactory knowledge 

 of the tidal currents at any locality, it is necessary to make observa- 

 tions at intervals throughout a twelve-hour period, to insure read- 

 ings for both flood and ebb, because the time of turning of the tide 

 at the bottom often difters by a considerable period from the time 

 of slack water on the surface. Nevertheless, our few isolated observa- 

 tions are worth passing notice because they are the first attempts to 

 measure the bottom currents of the Gulf of ]Maine with modern instru- 

 ments. The diagrams (fig. 38) illustrate the considerable strength of 

 the bottom currents even in the western side of the Gulf; and in the 

 northeastern part, for example over German Bank, they are even 

 stronger. 



The only region where enough observations were taken to allow a 

 tentative statement of the relations of bottom to surface currents is 

 the northern half of ^Massachusetts Bay (Stations 1, 2, 4, 5, 6). The 

 surface current flows into this part of the Bay toward northwest and 

 west at the height of the flood (Station 5) turning at least one half hour 

 before the time of high water at Gloucester, and flowing easterly 

 during the first half of the ebb (Stations 1 and 4). We made no records 

 for the last three hours of the ebb. A few miles further off shore the 

 direction at mid-ebb was southeast (Station 2) ; and in the centre of 

 the Bay (Station 6) N. N. E. (all bearings being magnetic). In the 

 southern half of the Bay the flood current ran toward the southwest, 

 the ebb toward the northeast. These observations are not sufficiently 

 extensive to show whether or not there is any dominant drift along- 

 shore. But tidal records taken by the U. S. Coast Survey at the 

 mouth of the Bay suggest that it may be occupied by an eddy-like 

 circulation flowing slowly from north to south, there being a decided 

 drift to the northwest near Cape Ann, with an easterly movement 

 on Stellwagen bank and near Race Point (U. S. Coast Pilot, part 

 1 and 2, 1911, p. 151). The bottom currents in Massachusetts Bay 

 dift'er very noticeably from the surface ones (fig. 38) not only in being 

 as a rule weaker, but in flowing in a different direction. At all the 

 stations in the central and northern part of the Bay, the bottom flow 

 was easterly, the records being made a few minutes before high water 

 (Station 1), tv\o-hour ebb (Station 4), mid-ebb (Station G), and early 

 flood (Station 5). This data, so far as it goes, suggests that if there 

 be any tidal flow to the west on the bottom it must be restricted to 



