80 
MR. II. N. DICKSON ON THE CIRCULATION OF THE 
lines were then transferred, point by point, to blank maps, reprints of part of the 
Polar chart used in the “ Challenger ” Ileports. These were then photographed and a 
set of prints coloured. From these Plates 1-4 liave been prepared. In numbering 
the lines on the Salinity Maps the first figure and the decimal point have been omitted 
for all salinities over 30'00 pro mille —thus 34'5 appears as 45, and so on. Salinities 
below 30'0 are given in full. The C(dours used ai-e as follows :— 
Salinity 36'0 or 
ovei’. 
dark blue. 
„ 35-0 to 
36-0. . 
iniddle blue 
•34-0 „ 
35-0. . 
liolit blue. 
33-0 „ 
34-0. . 
dark green. 
32-0 „ 
33-0. . 
lio-ht green. 
o O 
31-0 „ 
32-0. . 
dark red. 
30-0 „ 
31-0 . 
middle red. 
,, Under 
30-0 . 
light red. 
tem})erature is :— 
Over 25° 
■ lark red. 
20° to 25° . 
= . . 
light red. 
15° „ 20° . 
yellow. 
10° „ 15° . 
• 
green. 
5° „ 10° . 
light blue. 
0° „ 5° . 
middle blue. 
Below 0° . 
dark blue. 
In both the Temperature and Salinity Maps intermediate lines have been drawn 
where the observations seemed specially well able to define them, or when they 
seemed to throw additional light on the distril)ution (36). 
IV. 27/e Distribution of Teiiiperuturc and SaJimtij m the Surface Waters. 
January, 1896.—The observations for this inonth are limited to an area bounded 
by the 40th parallel and a line joining the Newfoundland Banks and the Faeroe 
Isles. The isothermal of 15° appears north of 40° N. lat. between the coast of 
Portugal and 35° W. long., and again between 60° and 65° AV.—the mean position of 
the axis of the Gulf Stream (37). The 10° isothermal cuts the 40th parallel in 50° W., 
and again in about'60° AV., further defining the head of the Gulf Stream ; the obser¬ 
vations do not define the course of the 10° line between 40° and 50° AV., but at 40° it 
reappears in 50° N. lat., following that parallel to about 22° AV., where it swerves up 
to 55° N. to enclose an area of relatively warm water S.AV. of the British Isles, 
turning soutli again some distance from their western coasts, and just touching the 
S.AV. point of Ireland. Between the two areas outlined l)y the 10° isothermal an 
area of cold water extends S.E. from the Newfoundland Banks, the line of 5° runs to 
about lat. 48° N., long. 43° AV., and then turns AA^., keeping well to the south of 
