106 
MR. H. N. DICKSON ON THE CIRCULATION OF THE 
60° N., forms during winter part of a cyclonic movement, resulting in a southerly and 
south-easterly drift on the western side, and a northerly drift on the eastern side. In 
the lower latitudes, about 40° N., the easterly movement is comparatively weak. The 
northerly movement in the easterly half of the area is considerable, but it is hampered 
by the configuration of the land—the Faeroe Isles, Iceland, Greenland, &c., hence the 
water tends to spread widely over the surface northward and north-westward, hut 
stream currents of any marked degree of energy are not developed. Hence there is a 
tendency at the end of winter towards uniform distribution of salinity and tem¬ 
perature, which is aided by a diminution in the supplies of Polar water. 
In spring the north and south comj)onents become less marked, and the easterly 
movement becomes stronger everywhere south of lat. 50° N., the increase being most 
noticeable in the lowest latitudes. The greater angle now made by the drift with 
the European cgast line causes increased “ banking-up ” of water against the land, 
and this Avater escapes by stream currents running northward and soutliAvard. The 
total discharge of these streams must depend on the rate and volume of the 
easterly drift, and the proportions discharged to north and south on the angle 
made by the drift with the coast. The direction of drift is probably always someAvhat 
towards the north, but the resistance due to the configuration of the land and to the 
influence of the earth’s rotation hinders the development of a northward stream 
sufiicient to carry off the Avater as fast as it accumulates, and the banked-up Avater 
tends also to sink beloAv the surface, causing the high temperatures ohsei’A'ed at Ioav 
levels in the Eastern Atlantic (41), and to accumulate further AvestAAmrd and north- 
Avestward, floAAnng out AAdiereA^er opportunity presents itself, as in the branches of the 
Irmino'er current. 
The northward discharge of Atlantic Avater from the loAver latitudes is therefore 
greater during the months of spring and summer, Avhen a stream current, independent 
of the local surface drift, sets nortliAAnrd betAveen Scotland and Iceland, attaining its 
greatest strength in the Faeroe-Shetland Channel, and haAung marked inductiA'e 
effects on the Polar bottom AAnter at the Wyville-Thomson Ridge (42). 
As the summer progresses, the drift circulation in the higher latitudes becomes 
Aveaker, but after midsummer the increased strength of the current from the south is 
replied to by an enormous delivery of Polar AAnter—first and chiefly from the area 
between the east and north-east of Iceland and Jan MaAmn, then later, as the ice 
breaks up, from the Polar current east of Greenland. The Labrador current also 
increases largely in volume, but a greater proportion ot this increase is likely to be 
due to melting of ice by the AA'-arm air sent uj) by the cyclonic circulation deA’eloped 
over the continent of North America. 
Except in the case of the Iceland—Jan Mayen Stream, AAliich deAmlops the features 
of a stream current of great energy, for reasons recently set forth by Petterssox (43), 
the Polar Avater forms lai'ge pools of fresh AA’ater to the east of the southern part of 
Greenland, and ofi' the Labrador coast, Avhere it seems to collect in a comparatiA'ely 
