REPOUT ON OCEANIC CIRCULATION. 
9 
wards, the rate of propagation being so slight as to be regarded rather as a slow creep than 
as a distinctly recognisable movement of the water. It is evident that the increase of 
temperature from the bottom of the ocean to the surface is due to the slow descent of 
the warmer water of the surface carrying downwards their higher temperature to 
greater depths. 
The following mean temperatures, calculated from the whole of the observations in 
all latitudes for the different depths, show the rate of diminution of the temperature 
downwards : — 
Depth in 
Fathoms. 
Temperature. 
Depth in 
Fathoms. 
Temperature. 
100 
60° -7 
900 
36°-8 
200 
50° -1 
1000 
36°-5 
300 
44°-7 
1100 
36°-l 
400 
41°-8 
1200 
35°-8 
500 
40°-l 
1300 
35°-6 
600 
39°-0 
1400 
35°-4 
700 
38°-l 
1500 
35°-3 
800 
37°-3 
2200 
35°-2 
Thus the fall of temperature from 100 fathoms to 2200 fathoms is 25°'5, and of 
this there is a fall of 10° ‘6 from 100 to 200 fathoms. For each successive 100 fathoms 
the falls of temperature are 5°'4, 2°‘9, 1°‘7, 1°T, 0°‘9, 0°’8, 0°'5, 0°‘3, 0°’4, 0°’3, 0°'2, 
0°'2, and 0°T, and for the 700 fathoms from 1500 to 2200 fathoms the mean fall is 
only the tenth of a degree. 
Prevailing Winds over the Ocean. 
These will be best studied in detail by referring to the Report on Atmospheric 
Circulation, pp. 48—69, and the maps 27—52, which show the isobaric lines and prevail- 
ing winds of the globe for the months and the year. In these maps the general 
movement of the atmosphere over the different oceans through the months of the year 
is clearly shown. The outstanding features of the circulation of the atmosphere bearing 
on this discussion will be seen in an examination of the prevailing winds in January 
and July, 
January . — In the North Atlantic, north of about lat, 35° N, atmospheric circulation 
is ruled by the low pressure about Iceland, in conjunction with the high pressure over 
North America on the one hand and Eurasia on the other. From this geographical 
distribution of the mass of the earth’s atmosphere, it inevitably follows that over the 
east coast of America the prevailing winds are north-westerly, and over Western Europe 
south-westerly. Hence the prevailing winds at this season blow the surface waters of 
(PHYS. CHEM. CHALL. EXP. — PART VIII. — 1895.) 2 
