542 NATURE 
[Jury 23, 1914 
explanation of this periodical variation would be, that 
the Gulf Stream kas a maximum velocity in the spring 
and a minimum period in the autumn, but Dr. 
Nansen is of opinion, that it is self-evident that the 
dilution of the surface water due to the precipitation 
during the summer in connection with vertical circu- 
lation during the winter, gives the simplest explana- 
tion of this seasonal variation. 
Krummel has termed that part of the Gulf Stream 
passing Section I. of the Frithjof cruise across the 
Rockall Channel and the Rockall Bank, the ‘Irish 
current.” Its waters are easily distinguished by the 
comparatively high salinities and temperature. “The 
section proves that the greater part of the water- 
masses, carried north-eastwards by the Irish current, 
passes through the Rockall Channel, between the 
continental shelf off Icelanc and the Rockall Bank, 
while only a small portion of the water with the 
highest salinities (above 35:30 per cent.) occurs west 
of the Rockall Bank, and seems to have no distinct 
northward movement.’’ It is obvious that it is a 
continuation of this current through the Rockall 
Channel which flows through the Faeroe-Shetland 
Channel. Amundsen’s observations in June and July 
also bear this out. These important recent Nor- 
wegian observations are confirmatory of the Porcu- 
pine observations of 1869. Dr. Nansen states that 
the Scottish series of salinity observations in August, 
1910, from the Faeroe-Shetland Channel, taken in the 
same month, have often some “‘inaccurate values,” 
and may be too high. Authority for this statement 
would have been desirable and also for the further 
criticism of the Scottish stations 19C and 14A of 
May, 1910, for it does not always follow that even 
‘very great irregularities ’’ indicate erroneous observa- 
tions, however inconvenient they may be to our 
theories. 
It is a fashion of the present day to attempt 
to obliterate the general term ‘‘Gulf Stream,” 
and Dr. Nansen follows this plan, but the 
fact remains that there is a continuous move- 
ment of the surface waters of the sea which 
is capable of carrying an object from the West 
Indies to Spitsbergen, and ‘‘Gulf Stream’’ remains a 
useful name for this continuous flow of water, called 
by recent investigators by different names in different 
regions. There is no doubt that the “Gulf Stream” 
is due to many factors, and not solely due to that 
initial impulse the waters have as they leave the Gulf 
of Mexico, but why not continue to use this useful 
term which defines this remarkable series of pheno- 
mena as a whole, at the same time recognising the 
different factors that cause it to exist. The statement 
that the Gulf Stream off western British coasts ‘‘is 
to a very great extent a current coming from the 
south, along the continental slope west of Europe,” 
is by no means new, and does not obliterate the main 
phenomenon referred to. The point of interest in the 
Norwegian observations is not that the current de- 
scribed by Rennell in 1793 flows northward, but that 
this current flows at quite a considerable depth, and 
not only at the surface, a very important addition to 
our knowledge of the Rennell current; also, that it 
seems to consist very largely of Mediterranean water. 
But in this connection, it should not be forgotten 
that about twenty years ago Buchan pointed out that 
the influence of the warm undercurrent from the 
Mediterranean is clearly apparent in the Atlantic Ocean 
at a depth of soo fathoms, and that ‘‘ beyond this 
depth, its great influence is felt over nearly the whole 
breadth of the Atlantic to at least about 1000 
fathoms.” ? 
It is a sweeping statement to say that ‘‘most lead- 
‘ = : 
2 Report on Ocean Circulation. 
Reports, 1895.) 
NO. 2334, VOL. 93] 
By Dr. Alex. Buchan. (Challenger 
ing oceanographers have taken it for granted that the 
currents of the surface layers were practically the 
same, at least as to direction, as those of the deeper 
strata,’ and that they study chiefly surface observa- 
tions, and think ‘‘ that all oceanic currents are chiefly, 
if not entirely, created by the winds,” that they do not 
understand the effect of the earth’s rotation, and have 
not appreciated the value of vertical sections of the 
ocean to elucidate horizontal movements of the water.” 
Carpenter, before the Challenger sailed, strongly 
advocated the doctrine of vertical ocean circulation 
sustained by opposition of temperature, and while 
Buchanan used vertical sections so early as 1877* ina 
paper entitled ‘‘ Distribution of Salt in the Ocean as 
Indicated by the Specific Gravity of its Waters,” where 
a vertical section through the Atlantic Ocean from 
30° N. to 30° S. is given. Subsequently Buchanan 
used vertical sections in his report on the specific 
gravity of ocean water, which was published in 1884 
in vol. i. (Chemistry and Physics) in the Challenger 
reports. In the same volume there appears a ‘‘ Report 
on Deep Sea Temperature Observations,”’ obtained by 
the officers of H.M.S. Challenger, where there are 
258 plates all representing vertical sections. In fact, 
no efficient oceanographer considers these physical 
questions without the use of vertical sections; neither 
would he assert that all oceanic currents are entirely 
created by wind, nor will he deny that they are very 
largely created by wind. Wind, specific gravity, tem- 
perature, and rotation of the earth are all among the 
many factors which influence oceanic circulation, both 
vertical and horizontal, and none of these should be 
considered apart from the others if satisfactory results 
are to be arrived at. 
Dr. Nansen considers it difficult to draw any certain 
conclusions as regards the annual variations in the 
temperature of the Irish current owing to insufficient 
material of observations from previous years. The 
observations seem, however, to prove that there have 
been no great variations in those few years. 
The temperature of the Irmiger current to the west 
of Iceland was warmest in 1896, less warm in 1895, 
1904, and 1903. There are also similar variations in 
the sea south of Iceland, but the conclusions are less 
trustworthy, because the sea is shallower and the 
frequent variations in depth may have a great influ- 
ence upon temperature even at short distances. These 
variations Dr. Nansen considers have an effect on the 
climate of Iceland. 
There appear to be continually very great changes 
in the position of ithe waters of the Faeroe-Shetland 
channel. Drs. Heiland-Hansen and Nansen conclude 
that great sub-surface boundary waves probably occur 
in the sea, and that ‘‘waves’’ seen in the many 
vertical sections of the Norwegian Sea may be due 
partly to such boundary waves, partly to horizontal 
vortex movements. 
The paper is a useful summary of all the observa- 
tions taken in these waters, besides those of the 
Frithjof expedition. ; 
Prof. Otto Pettersson and Commander C. F. Drech- 
sel urge systematic hydrographical and biological in- 
| vestigations of the whole of the Atlantic Ocean as 
one of the most important scientific and practical 
tasks of the future. As a beginning, synoptical recon- 
naissances at different seasons down to a depth of 
1000 metres, are recommended. The programme is 
drawn up in two heads :—(1) Investigation of coastal 
seas; (2) Transatlantic investigation cruises. Simul- 
taneous quarterly cruises are recommended, because 
this method of investigation has been recommended by 
recent geographical congresses, and has served as a 
basis for the investigation of northern seas and the 
Adriatic, for obtaining a comprehensive view of the 
3 Proc. R. G. S., March 12, 1877. 
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