4 
THE YOYAGE OF H.M.S. CHALLENGER. 
Lieutenant Baillie, Marine Superintendent of the Meteorological Office, obligingly 
re-drew for me a map, which he had prepared for Longman’s New Atlas, 1889, showing 
the mean annual temperature of the surface of the ocean. This map I have revised and 
amplified from observations, in which mean annual values are given, or data from which 
they can be calculated, published by the Meteorological Council of London, the Scottish 
Meteorological Society, and the German, Norwegian, Danish and Dutch Meteorological 
Institutes. The parts of the ocean thus dealt with are the Gulf of Mexico, the Atlantic 
from lat. 20° N. to 5° S., round the south of Greenland, round Iceland, Norwegian Sea 
and Arctic Ocean, North Sea, Mediterranean, Red Sea, Persian Gulf, west of Arabian Sea, 
east of Africa from Cape Guardafui and round the Cape to near Whalfisch Bay, and 
south of Australia. Since this discussion deals with the temperature at depths where 
the influence of season is virtually not felt, it was absolutely essential that it should start 
from the mean annual temperature of the surface. It is evident that mean temperature 
for a single month, or groups of months that do not represent an annual mean, would 
simply mislead. 
The specific gravities are those observed by the Challenger, reduced by Mr 
Buchanan, and published in the Challenger Reports, 1 together with the specific 
gravities given in the publications enumerated above as the sources from which 
the sea temperatures were obtained. The specific gravities given in the account 
of the Cruise of the “Novara” (Wien, 1862-65) have also been utilised, and also 
those given in the following publications of the Meteorological Council of London : 
Charts of Meteorological Data for Square 3, lat. 0°—10° N., long. 20°-30° W. ; 
Charts of Meteorological Data for Nine Ten-Degree Squares, lat. 20° N. to 10° 
S., long. 10° to 40° W. ; Meteorological Charts for the Ocean District adjacent 
to the Cape of Good Hope; and Twelfth Number of Meteorological Papers, published 
by authority of the Board of Trade. Professor Copeland has favoured me with a 
valuable unpublished series of specific gravities observed by him in the South 
Atlantic, west of Cape Colony, and thence round the Cape and through the Indian 
Ocean to a point a little to the south of Mauritius. When these observations of 
specific gravities had been entered in their respective positions on the maps, large 
sections of the ocean were found to be altogether unrepresented. These blanks, 
however, have been very largely filled up through the courtesy of the Meteorological 
Council in placing at my service their rich storehouse of observations not yet published. 
With these data the specific gravity of the surface of the oceans is fairly well 
represented. 
14. Exploration of the Faroe Channel during the summer of 1880, in H.M.’s hired ship “ Knight Errant,” by 
Staff-Commander Tizard, R.N., and John Murray ( Proc. Roy. Soc. Edin., vol. xi. p. 63). 
15. Deep-Sea Exploration in Faroe Channel by H.M.S. “Triton” in 1882, commanded by Staff-Commander Tizard, 
R.N. (Admiralty Blue Book). 
1 Report on the Specific Gravity of Samples of Ocean Water, observed on board H.M.S. Challenger during the 
years 1873-76, by J. Y. Buchanan, M.A., F.R.S.E. (Phys. Cliem. Chall. Exp., pt. ii., 1883). 
