34 BULLETIN OF THE BUREAU OF FISHERIES. 
3. CURRENTS AND TIDES. 
The first currents which concern us are two of the great permanent streams which 
maintain the circulation of the ocean, namely, the Gulf Stream and the southwardly 
flowing Labrador Current. Off the Massachusetts coast, the Gulf Stream is first encoun- 
tered at a distance of about 85 nautical miles south of Marthas Vineyard and Nantucket; 
that is, just beyond the edge of the continental shelf. Its distance from shore varies from 
year to year, and even during lesser periods. It has been shown by Libbey (1895) that 
the Gulf Stream, during this part of its course, at least, presents by no means a regular 
outline in crosssection, but exhibits, on its coastal side, a wall having very roughly the 
contour of an inverted S. Its lower boundary, which Libbey identifies approximately 
with the 50° (F.) curve, sends a projection coastward between the adjacent colder zone 
and the bottom, while at a higher level the cold stratum referred to projects seaward 
into the midst of the warmer water of the Gulf Stream. (See Libbey’s fig. 1-21.) 
This brings about the result that throughout a narrow strip along the continental declivity 
the latter is bathed by warmer water than it would otherwise be exposed to, and con- 
sequently supports a different fauna. 
A not wholly convincing illustration of the dependence of the fauna of this section 
of the ocean upon the chance relations of these temperature zones is offered by the case 
of the well-known tilefish, which suddenly disappeared from the edge of the continental 
platform for a period of about 10 years. (See Collins, 1884; Verrill, 1884; Libbey, 1895; 
Bumpus, 1899.) Its extermination was first revealed by the presence, during the spring 
of 1882, of enormous numbers of the dead fishes floating upon the surface of the sea 
throughout a belt parallel to the coast and about 170 miles in length. At the same time 
Verrill (1884, p. 656) reported the “‘scarcity or absence of many of the species, especially 
of Crustacea, that were taken in the two previous years, in essentially the same localities 
and depths in vast numbers—several thousand at a time.’’ Verrill accounted for this 
wholesale destruction of life by the occurrence of a heavy storm, which he believed to 
have ‘‘foreced outward the very cold water that, even in summer, occupies the wide area 
of shallower sea, in less than 60 fathoms, along the coast, and thus caused a sudden 
lowering of the temperature along this narrow, comparatively warm zone, where the 
tilefish and the Crustacea referred to were formerly found.’’ Libbey has endeavored to 
correlate the reappearance of the tilefish, about 1892, with a change in the position of the 
50° curve; and, indeed, the first successful search for the fish after the catastrophe of 
1882 was suggested by the discovery of changed temperature conditions. 
But the influence of the Gulf Stream extends much nearer to the coast than the 
edge of the continental shelf, and without doubt affects our local faunal conditions. 
The presence nearly every year in Vineyard Sound of considerable masses of the Sar- 
gassum bacciferum, with its attendant fauna, shows that strong southerly winds may 
drive the surface water of the Gulf Stream as far as the mainland of Massachusetts.? 
And, apart from these occasional and obvious effects, it is probable that the warm current 
exerts a constant influence upon the coastal waters of southern New England, the two 
undergoing a certain degree of intermingling as a result of winds and tides. Indirectly, 
a The prevailing wind during the summer months blows from the southwest quadrant. From records kept for five years 
on the Vineyard Sound Lightship (Rathbun, 1887), southwesterly winds are found to be the most frequent ones during the months 
of April to September, inclusive. At Nantucket, also, according to the report of the Chief of the Weather Bureau for 1909-10, 
the prevailing direction of the wind from May to September, inclusive, is southwest. 
