SURFACE WATERS OF THE NORTH ATLANTIC OCEAN. 
C5 
North Sea. At the same time, the S^Yedish scientists, with the support of their 
government, made efforts to secure the co-operation of other nations interested in the 
regions under examination, which were so far successful that a preliminary recon- 
nrdssance consisting of four sets of observations, at three-monthly intervals, was 
made during 1893 and 1894 by expeditions sent out simultaneously by Sweden, 
Norway, Denmark, Germany, and Great Britain, These observations have been 
worked up and reported on Ijy the directors of the several expeditions, and the results 
have been combined in a number of important papers by Professor Petteesson (11). 
During 1891 and 1892 a Danish expedition made important investigations in the 
seas north of Iceland and east of Greenland, extending a line of soundings as far as 
Spitsbergen (12). 
Althongh no further joint investigations have been carried on since those of 1893 
and 1894, active work has been continued in nearly all the countries concerned. Tlie 
Danish cruiser ‘‘ IngolfV’ under the command of Commodore C. P. Wandel, made 
important investigations in the seas round Iceland and Greenland in 1895 and 
1896 (13), and the Danish Hydrographic Office has continued the ansdysis and prompt 
publication of observations of surface temperature and of the position of the ice in the 
northern seas traversed by its merchant ve.ssels (14). Investigations were begun by 
Norway, under the direction of Dr. Johan H.iort(15), in November, 1893, in time to 
take part in the later of the joint expeditions referred to above, and since then 
Dr. Hjoet has continued his researches, especially with reference to fishery questions, 
with conspicuous success. Besides these we have the valuable ol)servations made by 
the Nansen Expedition, and numerous observations have been made by yachts and 
other vessels cruising in high latitudes. Professor Petteesson and his colleagues 
have continued to follow tlie changes in the Skagerak and Kattegat. In 1896 some 
of the stations in the Faeroe-Shetland Channel visited by H.M.S. “ Jackal ” in the 
work of 1893-94, and some of the stations of the earlier expeditions near the 
Wyville-Thomson Ilidge, were re-visited by H.M.S. “ Pie.search ” (16). 
Many of these observations, althongh not made on a preconcerted plan, can ])e 
discussed together, and they form a fairly efiective continuation of the work r)f 
1893-94, pending a systematic inve.stigation of the wdiole area by international co¬ 
operation. 
In tracing the movements of oceanic waters, live elements may be taken into 
account :— 
1. Direct mea.suremeiit, either by current meter, or l)y the drift of floating bodies. 
Hiese measurements are practically restricted to surface movements, and they are 
attended by difficulties of two kinds ; single observations of current from a vessel 
may be made in merely local and temporary streams, and observations of ‘‘ drifters” 
may be affected by errors due to uncertainty of their }iath, tlie effect of local drifts in 
shifting them from one current to another, uncei’tainty as to the time ad which they 
are found, and so on. The first method gives valuable results where very large 
YOL. cxcvi.—A. 
K 
