102 
MR. H. N. DICKSON ON THE CIRCULATION OF THE 
description of the movements of the surface waters so tar as can be gathered from the 
charts :— 
In January, 1806, two surfaces of warm and salt water, one off the American 
coast and the other extending eastward from mid-Atlantic to the coast of Europe, 
were entirely separated from each other at the surface by a band of cold fresh water 
running south-eastward from Newfoundland to the parallel of 40° N. This band is 
evidently an offshoot from a large area occupying the whole of the region off the 
Labrador coast, and another band extends due east from this area. There was 
probably a third similar band south-east of Greenland, and certainly one east of 
Iceland. 
During the tAvo following months there Avas a persistent moA^ement eastAvard and 
slightly northAvard OA^er nearly the AAdiole distance between lat. 40° and 60° N. The 
result is the cutting off of the southern end of the cold fresh band from Newfound¬ 
land, and the banking up of Avarm salt Avater toAvards the eastern side in the lower 
latitudes. The greater part of this escapes northward, Imt to the north of lat. 50° N. 
it is overlaid by the colder, fresher Avater from the Lalirador coast, AA'hich has also 
moved eastAvaixl, and takes part in the noitherly drift moA'-ement as it neai'S the land 
(note the 8° isothermal and the 35'2 isohaline to the south of Iceland in February 
and March). 
In the month of April there is the first marked indication that the general easterly 
movement is losing strength in the higher latitudes. The easterly drift from 
Laljrador begins to retreat, or rather to ])e absorbed by mixing, and it shrinks 
rapidly all round its edge, giving the appearance of Avarm salt AAurter, moA'ing west- 
Avard, to the south of Iceland. Farther south there is not the same Aveakening of the 
eastAvard movement, Imt there is evidence, l)oth from temperature and salinity, that 
more AAxrter is making its escape south-eastAvard. 
At the same time (April and May) the soutliAvard moA’ement of the fresher AA'aters 
alono; the land Ijegins ao-ain. South-east of NeAvfoundland the hiolrer isohalines do 
not give AAury, but the loAver lines are croAvded together by an increase in the streams 
from the land. The area covered by this Avater shoAA's a great rise of temperature 
in May, and in June it expands soutliAvards and contracts eastAA’ard, indicating that 
it is then largely due to the AAmter from the Gulf of St. LaAvrence, Avhich rapidly 
becomes AAarrmer. 
All this time a strong curi’ent of cold fresh Avater I'uns south-eastAvard from the 
north and east of Iceland; tlie north-easterly drift from the Atlantic comes to the 
surface only on the east side of the Faeroe-Shetland Channel, and the 35 AA^ater 
appears ovei- a large part of tlie North Sea. This south-easterly current apparently 
covers a larger and lai'ger area as the spring progresses; the nortli-easterly drift gets 
narroAver and narroAver, and the fresher surface Acater extends AvestAvaixl along the 
south coast of Iceland, though this is, no doubt, partly due to increased outlloAv of 
Avater from the land. 
